[blindkid] pet dog: what size to adopt?

[Alison Stephens]

Our family is considering adopting a pet dog (not guide dog).  My 7 year old son is totally blind.  I also have two sighted tween boys.
I would rather get a small-medium dog, but one rescue group says that a small dog could be injured if my son accidentally steps on or sits on the dog.
Does anyone have insights into sizes of dogs?
Thanks,Alison