I know a lot of people that start late, I am one of them, and that didn't matter at all. You can go to tumbling classes specifically for your skill level so that you don't feel as bad. Even though I started late, I actually know how to do a lot more than my friends do now. Don't let being a beginner stop you or you will regret it!
Gymnastics isn't "more bar work," it's everything work. You will work all of your muscles and practice every discipline (Vault, Bars, Beam, Floor).
If it's just floor stuff you want to learn (cartwheels, handstands, walkovers, handsprings etc.) then yes, a tumbling class would be your best bet.
You might be a bit behind the other girls, but maybe not. They'll all be at different levels. They were all new too once! Anyway, what I've learned in my time at the gym is that everyone is super helpful, and they don't judge just because you haven't been in gymnastics since you were three years old.
Have fun! :)
I have taken tumbling, ballet, tap, jazz, showcase, hip hop, and contemporary for 11 years(I am 14) and I LOVE it tumbling works manly with cartwheels, back walkovers, back handsprings, ariels, and MUCH more. You could take private tumbling classes to speed you up a bit but don't push your self to hard or you can get hurt, which I have done trying to get my back handspring last year, I almost had it on the mat and I tried it in my yard when I got home which was a really bad idea! I ended up breaking my arm, because I missed my hands, so if you do take tumbling classes dont try anything going backwards besides backbends because it is really scary if you miss your hands. After my arm healed I had to learn how to do a back walkover again which I trouble getting in the first place. I think you should take them, and be sure to stretch before every class or you can pull a muscle which hurts pretty bad but I defiantly think you should.
you wont be behind! just go for it