We have the same issue, with DD12 a DYS and DSalmost8 not. The last couple of years, I have gone with her and left my husband home with my son for a "boy party" weekend. (I make lots of jokes about them practicing fart noises and eating hot dogs together.) He hasn't asked a lot of questions, really. They don't always go to the same events or camps or whatever, and it has rarely come up as an issue. I think it would be a much bigger deal if we brought him to Reno and he wasn't able to do workshops that DD was doing.
So my guess is that your best strategy is going to be to plan something fun for your DH and him to do while you are at the Summit, and focus his attention on that instead of on what his brother is doing.
