https://teenage.engineering/store/pocket-operators
I have a few of those, and heaps of my friends gat sucked deeply into playing with them at the expense of whatever they actually came over for. "Nah, I'm not hungry. You should all eat without me, I'll just finish tweaking this groove."
They're aimed (as the company name hints) as a little older than 3 year olds.
One hint for the OP, it's so cool how you can plug those toys into each other in a chain, and have them all sync - so the percussion, base, and melody can all be programmed on threee different POs, and automatically play together.