Just the fact that you're already making an effort to include your son & keep him feeling important means that you'll do fine :)
I think the best part about having an older child is that you can celebrate the new baby's milestones together. It's been so much more fun to see SS be just as excited for DS's first words, and learning to crawl, and stand. I love talking to SS about the things that DS is learning.
It's old news to their dad, who raised SS on his own for the first 18 months, so it's nice to have a little chatty buddy! Plus being a "chatty cathy" doesn't require any extra hands, lol.