We use an XR med during the day. For days with evening activities we use a small dose of a no -XR adderall

Try a half dose around 4pm.

We've had the best luck with Concerta -- it lasts about 10 or 11 hours for my son. We also recently added Intuniv, and we see a slight but discernible in the evenings (i.e., he is not quite as wound up at bedtime). That said, if he has something in the evening past 7 pm or so, I have a prescription for 5 mg Focalin (not XR), and I'll give him 1/2 of one of those pills just to get him through the event, but not impact his sleep.

Can you find a different troop that meets on the weekend?

Had the same experience with my DS. It's very tricky to balance all of this out. I think a lot of parents struggle with the same issue. I didn't let him have sleepovers with his friends because there was no way for me to manage his behavior late in the evening or early in the morning, plus the lack of sleep made for a disastrous next day. Fortunately, the stimulant that my DS was on did not really interfere with his sleep so I could give him a booster late in the afternoon and he would mostly be fine for bed around 9.

My child is on Adderal XR, and it seems like the "therapeutic benefit" wears off around 4 or 5, but the stimulant effect lasts until 10 or so. By this I mean that he's often acting very impulsively by dinner time, but I'm disinclined to give him a booster because he already can't get to sleep until 10 or 11, so he's really not getting enough sleep for his age. He has boy scout meetings a couple times a month at 7 pm., and they are just a disaster. There's also a few other things in the evening, although none as late as boy scouts. I hate to have him quit scouts, because he likes it and I've heard it's a good outlet for kids with ADHD, but it takes about a month off my life every time I take him to a meeting trying to manage his impulsivity and avoid the looks from all the other parents.
Has anyone found a solution for this? Are there other meds that might have a longer therapeutic effect but not keep him up so long? I'll talk to his psychiatrist, of course, but wanted to see if anyone had any lived experience on this front. Those evening hours are sooooo hard, and that's when all the activities are.