I'm gonna say smallish roland cube, or maybe the vox. You will NEED a headphone jack. Trust me and my three children on this point. Not that I don't LOVE my little Pro Jr. It's just not baby friendly in any room...
This little amp sounds GREAT at any volume, i played on not long ago and it really has some great clean and dirty tones. They are cheap, so i think its a no-brainer here.