I’m making a meatloaf my husband wants me to add mushrooms nm and peas my question is do I have to cook them first or not

If you have fresh peas, then I think I'd par-boil them. If I was doing this, I'd use frozen baby peas, I think. Then you can just mix them in with the meatloaf and bake it. Canned would just turn to mush.

Mushrooms have lots of water in them. I think I'd sauté them in a little butter to let some of the water render, then add them to the mix.