tricky - it would be a definite no to the drums for me, unless I had a shed at the end of a 200 foot garden and unicycles are unbelievably difficult - how about some circus skills lessons (I have no idea where you get those - I looked into it once but didn;t get anywhere). then if she likes it and gets good you could get her a unicycle. (or is this the wild dreams of a 3 year old to which you weren;t really expecting a serious answer...)