When our daughter, who is 5, showed interest in ballet, we enrolled at a local arts school, that offered two lessons a week. After several months I saw her losing interest and just after the end of June, after their end of year show/ production of Nutcracker she calmly told us that, they had had enough of ballet :) She seemed to feel like it was not enjoyable or fun.
Then recently at birthday parties of her school friends, I had the opportunity to chat with some other parents, and the common issue was that with school and the extra curricular activities and clubs, the children didn't get to have much free time.
(This was particularly the case for parents with more than one child)
I askd whether the kids ever get to just lie down on the floor, head in hands, and daydream ? and the answer was "no". It seemed ironic that although the parents were not happy about it, they didn't seem to compelled to change the situation either.
I think that, that time, is also important for children. We would like to make sure that she has that. I think a couple of extra curricular activities could be enough for 5-7 year olds. Particulary if it is something that they can be expressive with or burn up energy with. ( We saw that the discipline required in ballet, dulled her enthusiasm )
Our 5 year old has weekly swimming lessons at her school so it would be fine if she wanted to join the swimming club next year, which would be her first year of primary school, in addition to that I would wait and see if her current interest in music and dance continues, while she has started to show a particular interest in the piano, I don't think this is a signal for us to be signing her up for lessons just yet.
I believe that some good quality "free time" is valuable for all children (and for us too)