I have 6 kids, and they are all very musical. We have many different instruments, and love playing together. While looking around at a music store, we came across a Kalimba. My 7 year old loved it and so I decided to find an inexpensive one on amazon.
This 17 key kalimba piano by FluTune is perfect! It was less than $40 and sounds great. It is really easy to pick up and there are lots of YouTube videos to help out.
This kalimba came with key stickers, a tuning hammer, a bag and small study booklet.
So far my kids have played it each day since we got it, and now my 7 year old can take it in his room and play much quieter than being on the family piano. :-)