How much are the tickets ? And does one ticket include all the bumper cars and other stuff ? Or are those all separate?

Check this out: https://www.seekonkgrandprix.com/park-info/pricing/

There is an option for unlimited rides on all the different cars/options they have. Check out their website for more pricing info. There are several different price options.

no the cars are seperate

Seekonk Grand Prix Ticket Prices: https://www.seekonkgrandprix.com/park-info/pricing/