We did it Veteran's Day 2003. That was a great honor for us, in memory of my dad.
I don't think you need to be a family with kids, it's geared for anyone that wants to raise the flags. My DS was taught how to handle the flags with respect, the order that must be maintained in raising the flags, and that the American flag is raised the highest.
They are the only flags raised in WDW that visitors can help with. The flags are raised there in a ceremony because WL is part of Fort Wilderness.
Be sure to ask when you check-in, that gives you a better chance of having a day available. Last year we were on the waiting list, but nobody cancels.