Eggs are full of protein and the shells are a perfect calcium source. Just remember to NEVER let them recognise the eggs as eggs! Break them up, mash them down, crush the shells to tiny bits! If they know they are eggs they will start eating their own eggs after laying them and that's a habit...
I have looked everywhere for a xylophone or toy piano. Every darn kids toy, no matter the age bracket, is electronic! What is wrong with this world? Electronics for 4 month old human babies? Kids won't ever knew how to think for themselves.