I'd wait a few months until you give the littleone pumpkin. It has a lot of water and my vet says it acts asa bit of a laxative. Wait until after he's used to normalleafy green veggies like parsley or romaine.
I don't start introducing veggies till at least6 months of age, sometimes longer depending on the rabbit and how theirtummy is. And then I would start with romaine and see how they handleit, then introduce other veggies slowly.