Hi Magickduck,
To me, your wedding should be about you and your partner celebrating in the ways you like best, it's your day after all. But at the same time, if you want your family/friends to join you then it's nice to put some thought into being a good host and making the event something that they'll enjoy also.
If your family have already expressed concern about it being a kid friendly event, you have a couple of options:
1. Tell them that it's an adult event and no kids are allowed. Depending on how you handle it and what the parents are like, you'll get parents who say "Awesome, a night off!" and book a babysitter right away, or the parent who's closest to you will come along with the other staying home with the kids, or you'll get parents who are offended that you wouldn't invite their little darlings and stay home completely.
2. Make the whole thing kid friendly
3. Go the middle route and make the first half of the event kid friendly - they love to get dressed up and dance, so you can probably tailor the early part of the night to be enjoyable for all. Then at X o'clock you can transition into whatever less kid friendly music/activities you might want and have that be the point that the kids go home to bed, off to a babysitter, to a special area dedicated to them for playing a game or watching a DVD.