I don't think my baby has ever done the tongue thing. I am totally suspicious of baby books that put things in these stern, absolute terms - "All babies will mimic you if you push your tongue out, and they do this from birth! Yes, every single baby in the world. Yep."
My baby's first social smiles happened at about 8 weeks.He did "smile" in his sleep from birth, but the first time he looked at us and smiled and then watched our response was around two months. BUT, I think it's important to point out here that when new parents get very excited about the first social smiles, they're not seeing a social smile in the sense that adults exchange them. I would not expect a baby to see you walk into the room and burst out a grin this early. At two months or so, a social smile is mostly an experiment. "What happens when I do this? The big human face does that. Interesting... What happens if I smile at this bookcase? Nothing. Hmmm...."
All of that said, if you're worried about the smile and the tongue mimic thing, ask your pediatrician! It's not worth toughing it out when a quick conversation could put your mind at ease. However, I think there's a wide range of normal, and I bet your baby is right where he should be.