First year of play here. I don't particularly want to grind mini games to get the 2000 token prize. If I don't turn in my tokens this year, will I still have them for next year's fair?
No, the star tokens do not carry over to the next year's fair. Whatever you don't spend this year will just disappear.
It is worth knowing that you will be awarded a number of tokens according to the place you've scored in the showcase, ranging from 50 tokens for last place to 1000 tokens for first place. Since the festival doesn't automatically end once you start the showcase, you can see how many tokens you win from it before grinding away at the mini-games.