Hubble - dog behaviourist (and artist.. and part time bum.. and.. you get the picture, dog behaviour and art are my income earners though, being a bum not so much!
As far as toddlers waving food..
Not likely to cause an attack - however some dogs would take the food and some dogs wouldn't be that gentle about it either so little fingers could easily get nipped.
People should not be letting their dogs approach a child in a pushchair (or indeed any child not supervised AND asking if its ok to say hi to the dog etc) because simply, its rude, but yes putting the food away is a sensible safety precaution (it also means YOU have the food and if theres any doubt or the owner wont remove the dog.. heck, throw the food away so the dog goes after the food and you can leave!).
Food and dogs is a major issue when the dog has food of its own (or views the food as its own, ie, anything in its mouth, touching it or very close to it and not clearly someone elses, belongs to that dog) and someone tries to take it away.
Its a common issue because people (ahem, idiots) attempt to teach the dog that its OK for folk to take stuff off them by... taking stuff off them.
When the dog communicates its displeasure/fear over this, the dog is punished for that (how dare, bloody dog, etc) the dog learns not 'let people take your stuff' but 'don't growl it doesn't work' and you quickly end up with a dog who..
Doesnt like people approaching when they have stuff
Doesnt DARE growl or do anything to the adult owner who has punished it in the past
Is highly likely to bite without warning the next stranger or child who LOOKS as though they intend to take stuff, because people are clearly a threat now and won't listen but the dog doesn't fear the child/strange adult quite as much as they fear their owner.
Another mega risk with little uns and dogs is that kids under around 6 do NOT associate the growl with the horrible snarly toothy face, and they do not naturally associate the growl as being a bad thing at all.
In fact they see the nasty teethy face as a SMILE... and as the growl means nothing will continue to toddle towards the dog, reaching out for its face going 'doggy doggy doggy' to give it a cuddle..
The dogs face is of course then in close proximity to the childs face and you can fill in the rest of what happens without me spelling that out!
The best thing I think any non-dog owning (or actually ANY parent at all) parent can do is teach children some dog rules..
Stand still
Be quiet
Don't stare
Don't grab
To interact, touch the shoulder or chest, not the top of the head/face/back/tail - only when the owner has been asked... if no owner, NO TOUCH (that one trips people up, the child has been taught to ask the owner but in the absence of an owner, many children, particularly the very young won't automatically figure out that they CAN'T ask so mustn't touch!)
Unfortunately some parents teach their children to fear, run around screaming and worrying... and some actually encourage their children to run up to strange dogs, this is particularly common in children who have their own dog or a close relative has a dog they interact with frequently - kids don't understand that someone elses dog is NOT teh same as their own dog!
So the best way forward really is to acknowledge 'there are dogs, thats nice' but reward the child for taking their attention OFF the dog and putting it back on to the parent.
Which is exactly the same thing I teach with dogs (puppies)... there are children over there, have a treat, lets do a nice thing - seeing children = focus on ME good things come from ME...
So you don't end up wtih dogs/kids magnetised towards one another out of excitement/prediction of a reward for approaching/interacting.