We're in sorta the same situation with DS9. His current school has been wonderful and feels that a grade skip is in order, but left it up to us. We've decided to go ahead with it after much thought and worry. At the end of the day, it seems (for us anyway) that to do nothing is worse than to try something that may or may not be the 'right' thing. DS is in 3rd, but has been accelerated to 4th for this last quarter with the hope that any blanks could be filled in prior to the skip to 5th next year. DS is already telling us that the accelerated work is easy and school is still boring, but we're hopeful that the skip next year will bring a bit more challenge. If not, I guess we'll revisit everything again and go from there. What sucks is that we'll be starting all of this in a new school in a new state. I really hope the 1 grade skip will be sufficient.
I'm not sure that there are any black/white concrete answers for these types of situations. I think we just do the best we can with the info we have. Good luck.