I would talk to their friend's parents (unless they are part of the problem) and arrange lots of play dates. That way they don't feel they are loosing their friends, but rather gaining new ones that are on the same wave length, hopefully.
Did your children request the grade skip themselves? DD has always asked for more challenge, so it's been an easy sell to have harder classes. I would explain about how kids learn at different pace and their place is in this new grade. Since they are both doing it, they can share their experiences with each other. I would plan a little "graduation" dinner and then maybe take them somewhere special after first day of school.
Good job for advocating your children. It makes it that much easier for future parents of GT children to have the same option.
Jen
