I am all for allowing children to go to camps, adventures, etc during the summer but in this situation, I believe 7 weeks is too long right now. I could see a shorter trip for him if you could manage to fly him home in a reasonable time on a non-stop flight.
How would you feel if your mom sent you on a great opportunity, no doubt, but while you were gone she went through final prep for a new baby and when you got home, here is new baby? new family dynamic!
I can see some potential resentment of being "sent away" to be "out of mom's hair" so she can can rest, prep and deliver. This baby marks a huge change in his life as well. He needs a chance to bond with this baby and feel like his is an important part of this process.
Are there any options with low cost camps through Parks/Rec/Y? I know some schools have camps for children that are low costs.
I would look more in to some local options and helping him feel important to you and helping you prepare for this baby. Preparation is mental ad well as physical... Be there for him so he can communicate with you. He also needs mom right now because I am sure at 7, even if he is happy about a new baby, he also feels like he is losing a part of mom. Make this a positive experience for you both.
Best wishes and congratulations.