Hi,
No, having a couple of fam flight not necessary you have to commit a full PPL flight training.....althought it really depends on which flight school you go to.
The flight school i go to at Toronto-Buttonville, the school offer fam flight as many time as you want/can afford but you can still walk away after a few tries if you dont want to commit for licence training.
Please bear in mind that GA flight training can be very easy but it can also be very difficult at the same time. Because, to me, since I am a newbie (32hrs), flying requires both phyically and mentally ready when operating a plane. Although I can sense other members would like to detest my point. And I am not trying to scare anyone here, but you have to try to see if you like it, since everybody is different. For example, turbulence is some I still dislike and can be uncomfortable, since tossing and joted around for the entire flight in a small Piper is far different experience from being in a Commerical Airliner.
Go and give it a shot, if you have a true passion in flying you will eventually get over any fears(if any) and love it as well as addictive
Wish you the best of luck!
Feel free to ask me any questions, I will do the best to help!
Happy flying and fly safe!
Tom