He's two! That's very normal 2yo behavior, GT or no. Honest!
<reassuring pat on the back>
Don't worry. Most preschools expect little to no sitting quietly for a 3yo or even 4yo. And frankly, I wouldn't recommend that you even consider ones that expect more than a couple of minutes of sitting still and listening at a stretch. More than that's generally not a good idea for kids at that age. They should be up experiencing and doing for themselves. That's how kids under 5 (and often over 5!) learn best. A bit of circle/sharing time is the norm--and even that should be engaging and participatory!--and that's plenty.
When we were pre-K shopping, we visited just one school that was a sit-still-and-be-quiet kind of place, and I called it the "Stepford pre-K" since it looked like a school perfect for the movie! Scary creepy. After 15+ minutes of utter silence while the teacher read an entire LONG Dr. Suess book, my 3yo son read a word on the page aloud, and all the kids turned and stared at him. One little girl hushed him sternly. <shudder> CLEARLY not right for my kid...or anyone else's child that I know! My son said, "I didn't like that place, Mommy" when we visited. My reply: "Yeah, me neither!"
I'm always in favor of more choices rather than fewer, so I don't mean to bash options. But I think school programs are useless if they don't respect the way kids learn. Just look for pre-K programs that encourage your child to be himself and will ease him into a more formal structure, as most do, and you'll be fine.
