%vehicle = new Vehicle() { dataBlock = jeepVehicle; position = "24.5 -37 460"; };
I think you're defining something wrong with the jeep, like using a Vehicle object instead of a WheeledVehicle object.
Other stuff:
clientGroup.getObject(%i).clearInventory(); //clears the client's inventory
clientGroup.getObject(%i).hasWon = 0; //reset their win status
You should set the client to a variable so that you only have to call the getObject method once.
mFloor(getRandom(1,miniGameList.size));
No need for mFloor. getRandom returns an integer.
if(clientGroup.getObject(%i).player.mountVehicle == 0){//check if player isn't in a vehicle
clientGroup.getObject(%i).bwLose();
Again, set the client to a variable.
minigameList
This isn't a problem but just an fyi, there is a default version of this: minigameGroup.