We just did this last year, and moved schools so it was a double whammy for our son and it was certainly nerve racking so I know how your feeling! As aculady said above, the science camp seemed to be much older children , and I also think it would be a lot less structured than a class will be at school.
My son struggles with impulsiveness, and over the years it has gone from aggression ( in prek-k) when he got overly frustrated, to now just not being able to stop talking when necessary, and other smaller impulsive behaviors...but it progresses every year that he grows (thankfully, the first few years gave me a lot of grey hairs ). I think depending on where your son goes to school ( region ) 7 won't be a bad age for 2nd grade at all, he'll be with quite a few who will have turned 7 within a few months of him depending on birthdays and possibly maybe a year older...so not a huge gap. We found a little bit bigger gap when DS went into 3rd at 7 but it still wasn't overly huge (he was with kids anywhere from 8-10).
Just keep preparing him so the situation isn't totally foreign when he walks in on his first day. Will he get to go to a meet the teacher night before hand, where parents and students are in attendance? That might ease some anxiety over who he will be with for the year. It sounds like the school is willing to accomodate, and work with you and that is huge...I've worked with a school who was like that with my son, and one that isn't....it makes a world of difference! Good luck to your son, and know if it doesn't work out, you can always chose to have him go back to his original grade and figure out other ways to accelerate him until he is more ready for that type of jump but I think you'll find he'll settle in ok!
