I think 5/8" Oak dowels will hold up well. They are doing their best to keep him off of things but it only takes a split second.
I've also decided to forego the biscuits on the legs & use a 1/4" deep rabbit instead. Should be easier to make them that way & I like the idea of having a shoulder at that joint. Probably makes no difference stability wise. Just gives an extra 1/4" glue surface.