This little cutie isn't quite ready for lessons as his hands are too small, but he sure loves "helping" the big brothers!
In years past, I have taught piano and taken on young students - ages 4 to 6 is what I would consider a pretty young student. I have had success teaching only a handful of these children. Why? Well, one of the key ingredients in the success of a young learner is PARENTAL INVOLVEMENT. Oh yes, just as in most any other learning, parents are a vital part of success in learning music. When someone asked me to teach their young child I would let them know that really, the only way we would be successful is if they (the parent) were willing to spend two to three hours weekly sitting down one-on-one with their child at the piano. Some of my piano parents were willing to do that, and their child was incredibly successful and made progress. Others did not, or at least were not as consistent. Even my almost eight year old needs me to be available and close by during the majority of his practice time. If he knows I am listening, or in the room with him, he is more likely to work harder and stay focused. If I just set a timer (or not) and say, "Start practicing!" and walk out, he's more likely to play around doing glissandos and messing with the pedals. ;o) He says, "I like doing that!" Of course he does. It's fun! And I would love to say "go practice" so I can make dinner/do laundry/help other children with homework/etc. and have him make good progress. It just doesn't work as well that way.
You may say, " I just don't know anything about music!" To this I say, "Neither does your child!" Haha! Go to their lesson with them. Learn along with them. Beginning piano is easy and you can pick it up right along with your child. By the time they get to where you'll have to take lessons too to keep up, they will probably be to a point where you won't have to be at the piano with them all the time. You will know enough by then to be able to listen and know if they're making mistakes or not (especially if you're still attending their lessons).
I know that attending lessons (when you could be running to the post office or pharmacy) is hard. Especially if you have other children. So, it may not be feasible for you to be with them at lessons, but having an open dialogue with your child's teacher is essential. Making sure you are involved in the learning and practicing process will greatly increase your child's chance of success. Again, beginning piano isn't that hard, and you can probably teach yourself - and let your child help you as well. What fun for them to teach mom! :o)