Toddlers and second pregnancys what to be be careful of

Hey ladies so this is my second pregnancy o have a most three year old son. He is very excited about baby and is always grabbing my belly and laying on me unfortunately he's a little clumsy and I end up hurt. I am only nine weeks so I am still scared of a miscarriage since I had one before my son. Is there ways to help him be involved that won't end with a elbow in my pelvis?