I’m not sure this is helpful, but I would feel the same way. I’m not sure in my son’s case I would let him go – I know that sounds overly protective, and I would be especially torn because for my guy it’s really hard to make friends so I try and encourage him to go to anything he is invited to. Things I might consider are letting him go for the evening but picking him up before it’s really late if you think he’d be ok with that. You might also talk to his doctor to see if they can recommend a short acting med to supplement his normal meds for just this occasion. My son has trouble with his impulsivity after his meds wear off so he takes a short acting pill on the two days per week that he participates in an evening sport. The downside is that it can make it hard for him to get to sleep those nights but for a sleepover that might not be a big deal. Finally, I think you have to talk to the parents and find out how they feel about having him. If you send him and he acts in a way that surprises everyone, it could damage the friendships he has with these kiddos and that in the long term would be worse than him being disappointed about missing the sleepover. Just one mom’s opinion.