Very lovely plan. It flows nicely :)

Few Thoughts:
-I personally hate 2 story spaces. Your open foyer is right besides the kids loft. I can imagine the noise would be unbearable. Also toys and junk thrown over. It wouldn't be much money to extend the floor across that area.

-Since the kids are sharing the hall bath I would enclose the toilet and tub separately. Actually if there was a way to enclose the toilet by itself as well that would be even better. That way one kid could bathe and the other could still go to the restroom.

-Think about giving the bonus room access from upstairs as well. That way the kids could go in there to play or whatever without having to walk downstairs and through the house. This would also give them better access to their rooms after playing without tracking mess through the first floor.

I would reconfigure the area behind the garage where the closet, laundry room, and garage storage are. I would make a back door there and a small bathroom for the kids to come in and out of to use, get a drink , wash up, etc...when out playing.

Like your idea of closing off the two story room for another room.

My grown daughter told me she watched many movies that she wasn't supposed to watch with her dad and I by peeking over our loft, in our first house like that.

I didn't have a clue that she watched "predator" when she was 8, lol.

Nice house.

There are lots of nice things about the house! So these are just some observations...

Where is the back door? Is it into the family room? Just want to make sure you have a good path for kids playing in the yard to come in and use the restroom (and hopefully not tromp across a nice carpet.) Might not seem like much now, but I've been through this when DS had 14 middle school boys playing football in the back yard. I was glad they had a short walk, on tile, to get to the bathroom. Likewise for you if you're working in the yard and you come inside with dirty hands, muddy shoes etc.

The master WIC takes up lots of exterior wall space, so it takes away from having windows on that side. You might want to reconfigure it to be more of an interior space between the MB and the Mbath.

If you stay with a 2 story great room, be sure to ask the builder about air returns and/or a heated floor, so that all your heat doesn't stay up at the ceiling. (Do a search here and on the kitchens forum for some threads on this topic.) Keep in mind what others said about them being noisy. Also, whoever is in that left side bedroom on the 2nd floor will have to walk past an opening, visible to anyone in the great room, to get to the bathroom. My teenage DD would certainly rebel. And I'd want to use that 350 square feet for usuable space on the 2nd floor.

Be sure to post your plans, with dimensions and aisle sizes, on the kitchens forum too; they can help get a beautiful and functional layout. For example, right now if a kid at the breakfast table wants more milk, they walk through a work zone past the stove to get to the refrigerator. And someone at the sink will be butt to butt with someone at the stove, depending on the aisle size. It's a nice sized space so I think you can get a more functional layout.

Have fun!

I only had a chance to look at the first floor so far, but I suggest drawing furniture into the spaces (especially breakfast nook area) to make sure you have enough room. We have a very small table with 8 ft from the end of our cabinetry to wall and it is way too small for table and chairs and traffic path (used everytime we enter or exit the house. I push the table and chairs against the wall after every meal so we can pass by easily.

I also agree that with kids if there is a way you can have a door from mudroom to backyard it would save LOTS of cleaning in the future. A powder room here would be great, too. Take it or leave it, but my family is just like yours fast forward a couple of years - kids ages 7,5,&2. :) Actually, my husband drags in more junk after feeding and playing with our outside dog. He He!

I just looked at the second floor. I think you will have lots of room to make the bathroom configuration work for you if you use the space above the great room for a third bedroom. This should allow you to open up the bonus room to the rest of the second floor. If you are using the bonus room as a work from home office you may want to leave it separated, but most likely you will be using it as a playroom. We live in a ranch house right now with a playroom above our garage and the kids never want to play up there because it is away from everything else. If you have it separated from the bedroom areas, I am sure the same thing would happen. Of course, if you have a reason for it to be separate, you could always put in a "secret door" that looks like a bookcase from the bedroom side then you can use it either way. When you add the third bedroom upstairs, you could put a hall bath near the playroom and then a shared bath for the other two bedrooms. Then friends visiting in the playroom will have a convenient place to go to the bathroom.

We are just starting to build now after years of planning. It is amazing how much our plans have morphed over time. We will see if yours do the same. :)