How to prep a toddler

Sara • Momma to AAG 🧒🏻 💙 & CDG 👶🏻 💙

Hi all. My son will be 3.5 when baby number two arrives in June. We have been trying to prep him by talking with him and reading books. I also want to get a baby doll with accessories so he can start practicing helping. Any dolls/brands anyone can recommend? Any other ideas? Thanks!