I'm afraid "going vegan" is a social craze which may or may not last, and I don't think many "instant converts" realise how much attention they need to pay to exactly what they're eating. I've been lacto-ovo-vegetarian for 40+ years and I still find it challenging to make vegan food that's properly nourishing (B vitamins are the most difficult to provide, in my view, and processed sweets often contain gelatine from animal sources). You really do need to read package labels quite closely! It sounds as though your son and his ex don't really know much about bringing up a vegan child. Difficult for you to broach the topic with either of them, I imagine, so it's probably best to do the best you can when you're providing the food. I'd advise you to use a good search engine to surf for "vegan snacks for kids" - loads of recipes and advice out there. Avoid American recipe books, though, as US cooks seem to think sugar is a staple ingredient which should be put into everything (bread that tastes like cake, maple syrup on fried eggs, etc). Best of luck with this, and you can only hope your son's ex gets more conversant with the basic elements of a nourishing diet as time goes on.
