My Ds started and dropped several activities around that age. Soccer, figure skating, dance. We made them finish out the paid sessions/seasons. We wanted them to be active in some sport most of the year because it is healthy for them, but it was their choice to stay in or drop a sport. Exploring a lot of options was okay. Eventually they found things they liked (but didn't really settle in until middle school). The only thing we insisted on was that they stick with swimming lessons until a certain level so they knew how to swim for safety reasons.
Even in high school, when D1 was elected captain of a sports team in her sophomore year, but it was a sport she did not love and she wanted to drop it, we let her do that at the end of the season. In retrospect (she is 20 now), it was MUCH better to let her follow her interests, and that was a good decision. She was captain of the team in a different (beloved) sport, and had many other activities. We also took her out of another sport (once) in the middle of a season because of grade issues. The coach was very understanding. She never went back to that sport, but that was also okay, it was early in high school when she was still exploring her options. Fixed the grade problem, too
One other thing to consider is that many activities are 1-2 days a week when your kids are small. As they get older, the time commitment grows, and it becomes VERY painful around 9th grade or so to decide what to drop (scouts, 4H, piano, multiple sports, chess club). And there are a whole host of new opportunities in high school (debate, speech, quiz bowl, drama, etc.). So I wouldn't worry too much about having them stick to activities past a given season/paid session. We were much more careful about limiting the number of activities D2 got into and making her choose between them as new things came up so she didn't have a lot of stuff to drop the first year of high school and had some room in her schedule to try new things. Her transition to high school was much smoother because we were more careful about loading up activities in lower and middle schoool.
