Hardwood Blocks

I have a series of wooden blocks with pictures on them abc CUTTING. I plan to buy premade blocks of hardwood, but I'm not sure what type of paint / spray to use on the outside to seal that will not be harmful to children if they put in their mouths. Does any non-toxic sealer work? I know that people do, but I'm not sure what they use!

I know Mod Podge is non-toxic. This should be sufficient.

seek advice from a paint store.