Your son is far too young to interact with a puppy, let alone a small yorkie. Be aware that you will need to monitor them at all times and never leave them alone together.
No. one reason for dogs being dumped is they "bit my child", usually because the child has seriously provoked the poor dog by pulling ears, tails, bopping with toy, picking up, etc.
If I were you, I would wait until my child is at least 8 or so and understand how to treat a dog before getting one.
Puppies and small children do not do well together.
There is not "quick" way to potty train a dog, most reliable is crate training, but puppies don't really have complete elimination control until they are at least 6 months old - it's hit or miss and a lot of work until then.
You can't keep your child out of the dog food or water unless you keep the child away from the area.
You are really not thinking this through - it will be a major job for you if you get a dog while your child is this young.
If you must have a dog, go to the shelters and ask if they have a decent size dog that is used to kids and puts up with them. A yorkie is a disaster waiting to happen.