Park WIFI can be OK but often is not, the more people that try to use it the worse it gets. Most folks these days are going with call phone hotspots. Either Verizon (the best) or ATT are favored. We use Visible which is on the Verizon cell phone system. A good plan is to put one person on Verizon and the other on ATT to provide a backup. I have rarely not had service even when boondocking. You will want a cell phone booster system.
Visible costs $40/month and has 'unlimited' data. We generally use 30+ GB/mo and have had no trouble so far. If you plan to watch movies all the time or otherwise burn thru a bunch of GB then I'm not sure how it would work. There are other services, the major companies have killed most of their cheap offerings. Lots of these small companies fail in a few months leaving up up the river, de-paddled.