if you have a trader joe's in your area, plantain chips and the freeze dried fruit are good toddler snacks. The fruit is good too b/c it melts in the mouth and is pretty easy for little ones who don't have a lot of teeth. Also dried fruit like raisins, blueberries, apples can be good depending on what sort of things they can chew.
I also LOVE the homemade larabars from Kitchen Stewardship. Way tastier than the packaged ones, IMO. I love zesty cranberry and cherry almond.
Bananas, apple slices, cheese, hard boild eggs, meat is a good idea too, although I never think of it as an on-the-go snack - but why not?
Chopped chicken would be pretty toddler friendly, I think. As well as deli meat (I buy Hormel naturals without the nitrates/ites.)
oh, I think a chopped up plain omelet (or scrambled eggs) could work too.