We've had a pop up trundle for 25 years...it has a standard twin mattress. We've never had any problems with it and it has been used by a fair amount of guests over the years.

Our daybed/trundle has a trundle that rolls out, not pops up.
Our old house had a lot of extra bedrooms on the third floor, so it made sense to outfit them for a lot of different configurations of guests. I never like daybeds aesthetically, but functionally they are hard to beat.

If it's for your grandniece, perhaps an aerobed? Then you can put it anywhere she wants to sleep.

We have an x-long twin bed with a regular-length pop-up trundle, the trundle is not at all flimsy and works very well.

I'll let you know next week after my tall and 180 lb teen son gets to sleep on my parents daybed/trundle. The last time he slept on it was 6 years ago and he was much smaller!

The lake house my family rented had a daybed with trundle that was a rollout vs. popup. I would say OK for kids but for adults maybe not so much. I think we would have preferred two separate twin beds. I don't know if the pop-up trundle would be better since the rollout is so low to the ground.

We have a twin bed w/ trundle in our beach house and it has been used by people aged 9 to 50! It is just like a regular twin bed -- it rolls out and pops up to regular-bed height. It doesn't have a box spring, of course, but otherwise it's just like sleeping on a regular twin bed.

This is all good news. I don't know why I had it in my mind that a pop up would be flimsy. I really have no experience with them. The daybed-trundle set up would work the best for this room. I suppose if people come to stay and someone wants to sleep elsewhere (perhaps the hall or my closet??) the mattress from the trundle could be moved.

An aerobed may be the quick answer although my experience with them is that it's like sleeping on a rubber raft and they smell of rubber. They also seem to spring leaks rather quickly and the sleeper wakes up on the hard floor! Still, it is an interim solution.

Thanks for your help.

The pop up frame we have is all metal...just like a regular metal bed frame...not flimsy at all. Of course, I would never use it on a permanent basis as a regular bed...but for occasional guests for a few days it is just fine...and much more preferable to the roll out kind which are low to the ground and more perhaps more difficult for adult guests to manage.

After having it for about 5 years, I just sold the daybed with pop-up trundle in our guest room and replaced it with a queen size aero bed from Frontgate. Why? Several reasons, really. (1) my adult guests, especially our adult son who ( at 6' tall and 190 lbs) is neither very tall or heavy, told me the oak sides and back of the daybed made it somewhat uncomfortable to sleep on. DS actually got a black eye during one visit from hitting his face on the daybed's side arm, which was oak, (2) to allow for a decent mattress on the trundle, the height of the daybed made it really too high to be used comfortably as a sofa when company wasn't here, as this is my study and workroom most of the time. (3) the pop-up trundle did not stay in place next to the trundle, nor were the mattresses the same height for a couple to use together. Used as two twin beds, the layout of the room made for an awkward, cluttered mess IMO.
But, if you don't intend to use it as a sofa when company isn't there; if it will mainly be used by children or small adults and if you have room to pull out the trundle comfortably, I think it might work very well for you.
Lynn

An aerobed may be the quick answer although my experience with them is that it's like sleeping on a rubber raft and they smell of rubber.

I think you're a little behind the times on this! We just got the Serta "tall" self-inflating (and deflating) air bed and it neither leaks, nor smells of rubber. (lynn, Frontgate was out of stock on the airbed-on-frame and we needed something soon LOL!). We did get a fiber-fill thingie to put on top.

Our Dresher daybed is nearly 30 years old and it's in our tiny guestroom. The trundle frame is metal, rolls out, pops up and is the same height as 2 twin beds. We've used it for kids, sleepovers, teens and even a married couple who pushed them together and used a king top sheet and comforter. When ny nephew stayed with us he was transitioning from a crib to a regular bed and we pulled the trundle out but left it folded on the ground so if he fell out of bed he'd have a nice soft landing.

I wouldn't want to use one regularly only because it's a little harder to make the bed.

So, is a Serta inflatable mattress much better than the Aerobeds? Yes, I am definitely out of the loop on these things.

I'd rather buy a decent inflatable than a daybed, at least for now. It's nice to know the trundle option is still a good one.

Here is a link that might be useful: this one?

I am afraid to use my credit card at Target, so I am ordering a twin size from Amazon. I will take your advice and get a cover for it, too. Yay.

I know - I used my CC at Target during the "problem" period. Now I have to pay close attention to my accounts.

My parents just bought that same one. I used it when we visited a couple of weeks ago. It was comfortable BUT great call on the topper. I had layers of blankets that I slept ON TOP of because the bed just feels cold. I think sleeping on air will always have that.

I think a topper would alleviate that issue and it should be quite comfortable. :)

Would a regular mattress pad be good enough as a topper? I have a bunch of those and hate to buy another item to have around. Most of my mattress pads are queens, so I figure I can just wrap it around the entire air bed.

I have had two trundles that roll out and pop up. We loved them. We have occasional out of town guests, and no designated guest room so it was perfect when the kids were smaller. They didn't need two twin beds 90% of the time and their rooms aren't large. The pop up feature made the beds just like a conventional twin. I had large adult men sleep on them without complaints, they used regular mattresses (pillow tops are typically too tall).

Now that the kids are teens they all have full or queen beds so they just get moved to the basement when we have guests.

I think a regular mattress pad would alleviate the "sleeping on a rubber raft" issue!