OP, I would be very happy for my child to come to one of your parties :) I eat meat, but I would serve much the same as you did. I wouldn't dream of doing nutella sarnies, because there might be a child with a nut allergy, and I wouldn't do something like ham, because there might be a veggie, Jewish or Muslim child there. I would also personally be a little bit pissed off if you served chocolate spread sandwiches, etc., as I don't want my son eating stuff like that, even at a party. Even so, I wouldn't say a thing to you, I would thank you for your party and mean it.
What you provided was tasty, easy to eat, pretty plain (not an insult), and would fall into the remit of 'nice' food for most toddlers. If there are children there who are so fussy that their diet is extremely limited, then one of his or her parents should have a polite word with you beforehand. And if a child has been brought up with such a crap diet that what you served up seemed too weird or 'healthy', then the problem there lies with those parents, not you! (BTW, I am not talking about children who only eat beige or junky food, despite the best efforts of their parents, but kids whose parents purposely choose trashy food).
When I were a lass,
Mums didn't put out a huge variety of choice to try to cover every possible and potential dietary whim of every invitee. If you didn't like anything, it was tough shit, and you'd be told off by your own mum for being rude to your host.
If kids come back from a party having not eaten anything, you just feed them. What you don't do is text back some unnecessary, aggressive, illiterate text that is embarrassingly obvious in trying to make a point about you being vegetarian. A lot of idiots don't realise that, unless you're actually eating meat or fish at every meal, nearly everyone's diet is comprised of mostly veggie, or even vegan, food.
I think the very fact that she would lower herself to this behaviour means you pretty much don't have to worry about it. She is a knob, OP.