Looking for ideas on what to do with boiled egg yolks

My kids (under 4yo) absolutely love eating boiled eggs, but they don't eat the yolks. I hate throwing away so many, so I just don't make it for them as much as I used to, especially with the cost of eggs I dont like wasting half the product. However, it is a great way to get fast protein in them. So my question is, what can I do with the yolks to make them more appetizing or turn them into something else, besides egg salad??