When our boys were young, we let them bring friends and they had their own large tent. Our youngest enjoyed camping a lot more than our oldest. And it is that way to this day, at ages 26 and 22.
Maybe let your boys pick out board/card games to take with you. We brought a plastic bat and wiffle balls which drew other kids to our campsite like crazy. It still does. Now we have to wrap all the wiffle balls with duct tape because they hit them so dang hard. Horseshoes is another thing they are starting to enjoy.
BTW - We left the oldest home alone ONCE. We had to come home to get a few things we forgot and were able to stock our cooler with a lot of beer and wine coolers that my son and his friends had leftover from their first night alone. ;) Never left him home alone again.
Good luck to you!