We started a 3.5 year old so what someone else noted - to develop an ability to focus on something she wasn't dictating. The hard part you are right - is you taking the time to ensure they practice or it is pointless. It's been a good thing for her. We started the then 5.5 year old 6 months later so they'd get off on a more even footing. The younger one does better now that she is trying to best her sister or at least show her not to be shy. Ironically we thought the younger's love for music would rule out but the older is all math and patterns - so despite it being susuki - the older one figured out who to read sheet music in a day.
I can't tell you what is right in your case. For us, I grew up with susuki lessons and love music. The oldest needs something that doesn't happen perfectly without practice. The youngest needs something to force her to pay attention now at 4.5 our practice time is still a meger 10-12 minutes a day. So for us it is more a parenting - reinforcement tool of sorts. If they decide in a year to throw in the towel or we have to switch teachers and nobody wants to go forward... then we'll see. For now while there are the "no I don't want to practice" there is still a lot of "holy cow" did you hear what I did - a looks of self pride for failing, failing, getting it right. School may not offer a lot of opportunities to have to work hard at something before getting it right.
but overscheduling is definately something we try to avoid. our girls aren't much for a lot of sports at present...
so basically i'm not saying anything new here :-) sorry - more of the same. you can always wait for fall/winter to come to give it a try when there isn't so much draw for the outdoors (of course we live in a snowpile).
