Few listeners will be able to tell. After a while your left hand will develop a feel for where the notes might be expected to be. After a while, your right hand will be able to pick out the melody essentially by ear without having to pay so much attention to the notes on the page, thus allowing you to pay more attention to the left hands harmonies. These two trends will combine together to make playing easier and easier. Doing a little bit of playing by ear, and a little bit of sight reading new music, will help to strengthen these trends.
Children learn best by doing.
Let them goof with the keys while you play. Or let them make horrible sounds by themselves, and if they accidentally play something that sounds good, be sure to acknowledge it, so it will be more likely to occur in the future. My son by the age of 8 was playing well both by reading music, and by ear, without ever having had a lesson. He just tinkered around. Finding the Notes To make learning sheet music easier, take a staff of music, cut it up into little pieces, and tape the pieces to the appropriate key on the piano, right up next to the body so they won't be in the way.