How can I get my toddler not to feed my dog?

I know this is not a forum for asking parenting questions, but I was hoping to get some advice from other parents who have dogs. One of my dogs is getting chunky and she is on diet food. Not free-fed. She eats 2x a day. The problem is that my son (2 years old) feeds her all the time. Usually I gate her in a different room from him but if I don't she is right by his chair waiting for him to drop something. Any tips on training my toddler or dog? I'd like for him to not feed her and for her to not sit right by him waiting and staring.

I'm thinking about starting to raw feed my dogs. I am hoping raw feeding will help her be less food obsessed because it's all natural and not junk dog food meaning it'll help her feel more full. I have been doing research online. Is it really as easy as buying a cut of meat & bone/a chicken/fish and some veggies and just giving it to your dog? Any tips and suggestions would be helpful!

I have a 5 month old Border Collie & 1 year old Corgi.