I would be very worried as well. However, I’ve learned that I cannot keep my son from having childhood experiences due to my own fears of what might happen.
First, make sure your son wants to go to the party, and wants to stay all night. My son often wanted to, but would call to be picked up before time to go to sleep. After a couple of those instances, we started planning for him to go, but not sleep over. The other parents were always fine with that. He was 13 or 14 before he actually stayed the night with a friend.
After determining that he does want to go and does want to stay the night, determine what you can do to make it as successful as possible. Be honest with the hosting parent(s) and let them know he has ADHD and may have more energy later in the day as the excitement builds (you don’t have to talk medication with them). Let them know that it’s ok to call you if he wants to come home early. You can set the stage without making it sound like he will be a handful or a troublemaker.
Here’s more on sleepovers and ADHD:
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism