Is baby old enough for Wagon

I want to get a wagon for my Lo this summer. She will be 6 months in June and I also have a 3 year old who tires easily. We are a very active family, we go to the zoo weekly, the pool every day and tons of museums. What wagon do you guys recommend that’s nice and reasonably priced. Also is she too young for a wagon??? Should I make sure I only get one with seatbelts??? Help im so confused.