My opinion

What Schering said is right if your goal is for learning both performance and musical (or in general art) appreciation. If you goal is merely for musical appreciation, you don't need to put such an effort. But you still need to have your piano toned at least once a year to get the tone right, otherwise you are hurting your kids's ear. If you are really serious about musical appreciation (particularly classic musical), you need to go to professional concert to develop a good tastes. If you'r not serious about any of them, let your kids play whatever she/he likes.