Once you have the Tooth Chipper in Krustyland that's it. Just keep visiting to collect Tickets and play Sideshow You. Tickets can be exchanged for cash. Sideshow You pays out 5 donuts every 120 rounds (360 balloons popped).
There aren't a lot of specific Squidport tasks either. Once you have all the Boardwalk tiles finished, that's it. There's a lot more buildings and stuff you can put on the tiles other than the ones specifically designed for it, so you can expand your town onto it and make a little more room for buildings. I got the Yellow Submersible in 2 of my towns so I have a lot more tiles than you can craft at the Entrance. If you get the chance to buy it be sure to do so.