Outdoor sensory play is a fun and educational way for babies and toddlers to explore the world. Activities like digging in soil or feeling different textures promote hand-eye coordination and early science learning.
I really wish I could give you THE answer. Regrettably, thousands of years of human knowledge on this point has served up only this: It's a dang crapshoot. You have created two unique humans and sent them spinning off like tops into a very complex world. They may fight like cats and dogs as kids and become thick as thieves as adults, or they may be little buddies as kids and maintain (at best) a cool civility when forced to interact at weddings and funerals.
What makes me even crazier is that I know they can listen. I know this because they do all the time, mostly when they aren't supposed to. I can't tell you how many times I've been having an adult conversation with my husband and/or friends and my two children-who haven't listened to a word I've said all day-suddenly have very thoughtful and detailed questions