What is your take on when your kiddos do something you don't agree with at all, but it's important to them? How do you support their dreams when they are your nightmares?
My version of “things I don't agree with” may differ from a lot of other people's, but I definitely have a few. I don't care about haircuts (as long as it's clean and out of the kid's eyes) or fashions (as long as they're clean and not too revealing). I care a lot about my kids' taking responsibility for their own actions and owning up to them, and about their absolute truthfulness to us as their parents.
If the kid in question is one who has proven to be mostly trustworthy, and if whatever it is they want to do isn't illegal or hurtful to someone else, and if they are keeping things together pretty well otherwise (grades, prior commitments, etc.) then I will probably go ahead and let them do it. (I have been known to keep a clandestine eye on them if I'm nervous about their safety, however.)
To a certain extent you can circumscribe their movements but there are some things you don't get to decide for your kids no matter what age they are, such as what music moves them or who they like or who they love or what they want to study. You have to do the best you can to teach them to make good decisions, and then trust them to do so.
Other things are absolutely non-negotiable. I won't let them go to someone's house if a parent isn't home, I don't care why. I have a zero-tolerance policy about smoking, underage drinking or drug use. If one of them ever gets in a car with a driver who has been drinking, they'd better hope they die in a fiery crash - because if they do get home alive I will kill them.
Still, with six kids, we've gone through our share of stupid haircuts and colors (actually I love the colors!), friends I didn't like, Significant Others I didn't like, college majors I thought were silly, trips I felt were inadequately supervised, dropping out of college and marriage at a very young age. These are not necessarily the things I'd have chosen for them, but everyone survived. I have to trust that they're doing their best.
For me, the 18th birthday is a big dividing line. Once they're adults I try (with varying degrees of success, I admit) to keep my mouth shut unless they ask me what I think. Then I try really hard to state any objections mildly, once, and turn the conversation back to their thoughts on the matter.
Parents have a choice to make, and we don't get to make it just once; we have to keep making it every second we've got kids at home. Do we shelter them as best we can from everything that might hurt them until they're on their own? Or do we do the best we can to teach them morals, self-control and critical thinking and then let them reap what they sow?
There's no doubt that it's a juggling act; however, the fact that you're even asking the question shows that you're on the right track.