I've never used egg in rissoles or meatballs - just whizz up meat or fish with fresh herbs and seasoning, shape into balls and fry or bake... Add a few fresh breadcrumbs to lighten it if you like.
Chicken and apricot with fresh coriander go down really well, or salmon with dill, or whatever you and your LO like!
Weird how the minute you can't use something you can't do without it. We never cook with eggs, but I'm sure if I couldn't ever use them again I'd immediately be unable to think of anything to cook that didn't involve one
Good luck! x