Wanna ride a rollercoaster ?
The main interest of Paris is, of course, nice monuments and a romantic atmosphere but I you feel like riding a roller coaster you can two. There are some big parks around Paris, very easy to reach (even without a car) and I bet you know only one of them Don't worry I'll tell you about the others !
This is the one you may already known (at least you should know its name). Disneyland is one of the two most well known parks in the area of Paris. It's very easy to reach as it basically has it's own subway station (take the underground "RER A", 35mn from the very center of Paris you're at the gates of Disneyland !!). As far as I know they even used to sell tickets including the park entrance and the RER ticket Let's talk money by the way : it's about 50euros a day per person (of course it's "around" this, I'm not going to sum up here all their offers, if you want a complete sheet, check the official site ). The main characteristics you should remember are : it's easy to reach without a car, it's Disney (so kids will love it), and the only drawback is that some may find it a bit too much kid-oriented.
I bet you do not know this one yet ! It's the other one of the two most known parks around Paris (it's a draw with Disneyland). Maybe you already know who Asterix is ? If not : Asterix is a cartoon character, a French cartoon character, known worldwide. He lives at the time when the Roman empire had vanquished almost all Europe (but not his little village ) and he is damn funny ^^ ! What are the differences between Asterix park and Disneyland will you ask ? The first one is how you'll go there. To go to the Asterix park you have to have your own car, or to take the special bus that takes you from the center of Paris directly to the park. It's still very easy, but a bit less than going to Disneyland. Second major difference : insane roller coasters There are many things for kids, but they did not forget the adults (what Disneyland seems to have done sometimes). I highly recommend you the "Tonnerre de Zeus" which is supposed to be the highest/fastest/scariest roller coaster of the park ! And finally the best difference : it's cheaper than Disneyland (around 40 euros). To be honest with you, although in my heart it's a draw between the two parks (Disney and Asterix), if Asterix park had a subway station two, it would be my favorite one ! Check their website for yourself to find pieces of information I would not have given you here
The "Foire du Trone"
And finally the "Foire du Trone". Watch out : this one is not a park (i.e. : you'll pay for every attraction you'll do and not just one big fee at the entrance). It's quite known in Paris, as far as I know it's very very easy to go there (even more thant to Disneyland, I guess it's closer to the center of Paris). The only little problem is that I've never been there, so I can not really talk to you about it...so go and try it (only advice I can give you : be careful, some say that there are many pickpockets around there). Check the official site for yourself if you want to know more
As a conclusion I'd say that you really should go to one of the two big parks if you are around for more than a week, but do not forget that in parks food is always very expensive, so it may be a good idea to bring your own sandwiches (and if you want to warm up your sandwich making skills before you go, why not go to some good pick nick spots in paris some day before ?)