ummm your having you 2 year old son feed the dog that growls and snaps at him?
I think you need to teach her who the leader is and it should not be a 2year old, I'm far from knowing a lot, however; I can see there may be danger if you allow you son to keep charge of her.
You as the parent of both

she be incharge and fix the problem she is having with a trainer, books or from people here.
My second boy when I adopted him he was so nervouse around food he would growl at anyone that came near it, this I knew I had to stop, it made me even scared..... so I decided that I had to nip it, slowly, I FED HIM with food in my hand, for a little bit till he came to know me, I also, *some may find this very gross, I would say gently, nice, as he watched me put food in my mouth chewed it and have him eat it from my lips, if he went in like a purana I would move my face away spit out the food back on my hand and say nice, gentle, then repeat.
When I would feed him in the bowl I would lay beside his bowl when he ate, whispering it's ok little buddy he would look and carry on eating, then next step as food was put in bowl for him my hand would go inside his bowl, before he wanted to eat, and I would say mine, SIT wait, then ok and allow him to eat, when I saw he was respecting this.......then as he ate i would put my hand back inside his bowl, sturing it around a bit as he respectfully ate, I would pet him nicely and say good boy, this takes awhile but it did work, he is a very gentle soul now when it comes to his food, and it makes me feel better that He is more calm with food.
I don't recommend this for everyone, but it worked for us

and anything that helped my little man I was going to do.
Both boys could be eating side by side and if one finishes before the other and tries to go to the other dogs food I say, NO it's so and so's food you had yours, and they walk away,
also if people or kids are here, they could pass my boys food and dogs just look and carry on eating, this is a safe thing for everyone.
lol sorry for the long blahing