A search for tent rental will give you an idea of what is possible. Basically any size or configuration can be had. Find a local place and make a call to ask your questions.

You could get a pavilion without the sidewalls and use the heaters. It seems to me like a walled tent over your patio kind of spoils the fact that it is a patio. Maybe only use one side wall for the side where a cold wind is likely to be blowing in-- unless that wall would be where your view is. . .

But, yeah, they'll have three sided tents. That's what you'd see at outdoor fairs- craft or food booths.

A pavilion sounds ideal - I'll look into that. The yard is fairly protected, so cold wind probably isn't a factor as much as rain might be. I'd like to keep the the view of the pool, and the pavilion would make that possible.
Thanks!

I have rented tents three times for graduations and a surprise 40th. They have cathedral tents but we used the blue and white striped, or the yellow and white striped as it was not a formal occasion. We did put it up over the driveway, and di dnot need sides due to the time of the year but they were available for another charge. The sides won't ruin the atmosphere of your patio if you leave part of the patio open. It worked out really well. Since then we have built a garage but we have many fond memories under the tens. They have all different sizes available also. Just contact your Rent a Center.