What is it you wantthem to try? Volunteer TOGETHER at a food bank, get note pads and go to the park and draw what you see together, if they show an interest and want to improve, then get them lessons.
If you want them to get interested in music or dance - take them to some shows and get them excited. Want them in martial arts? Watch Karate Kid and take them to a tournament to let them see how it works.
Just do it. Heck, go out on the floor and look silly for them. Once they see you do it (even fail at it) they will be more likely to do it too :).
Encouragement. Make sure they realize that they do not have to be perfect at something, but as long as they give it a good shot.
Also, if they are reluctant about something, DO NOT sign them up for a year! You don't want to be stuck in a situation where you feel obligated to take your child to a thing for A YEAR and they HATE IT.
sorry no advice. i have the opposite problem. my children have so many interests & want to try everything.
We have gotten other kids to try different sports by inviting them to play with us. I have had kids that weren't interested in softball but invited them to one of our softball playdates (several girls come together and practice but still have fun) and liked it. One girl signed up and ended up being a really good player.
many of them are influenced by their peers so if you have a friend whose son or daughter plays a sport or does an activity, see if your child can go out and try it with them.
Almost every place has a free trial. We usually start with that and go from there. For sports go to a rec center and see what they have to offer. My boys must pick one activity per season; it can be music lessons, sports, karate, art classes, acting classes, etc.
Honestly our kids are in too many things and we have to scale back b/c they just can't do it all ;)