Any cyclists here? What age did you start riding with your little ones? Did you use the cart or the bike seat on the back?

We'll be going on vacation soon to a place where bike trails are a big attraction. Our little one will be 8 months old (she's sort of sitting up now at 6 months, I'm guessing she'll be a good sitter by then?). Will she be old enough, or should we skip renting bikes until she's in the toddler stage?