To boil the above comments into one dish, there are two parts to reliable and decently fast internet service:
1) The ISP (internet service provider) and your gateway or connection to the provider, and
2) How the signal from that connection is transmitted and received to/from your device - what you think of as "Wi-Fi" when it's wireless (Ethernet is most common when hard-wired).
A so-called wi-fi booster will only amplify the signal to/from the wi-fi router in use at the park. IT WILL NOT improve the park's internet connection in terms of speed or what others have referred to as bandwidth (think of it as how many lanes a highway has to carry traffic). If you spend hundreds on a device to improve the wi-fi connection with a crappy park internet service, you still have crappy park internet service.
The alternative is a 4G hot spot (as mentioned, some folks use their smartphones for this) that will provide internet service via your phone plan's 4G data service. There are also dedicated 4G hot-spots like the Verizon MiFi that we use. If you go this route, you will have to pay more for data, but you'll have much more reliable service and will be able to do anything except stream full-length HD movies (due to your data limitations and cost - not the technology).
I hope this helps.
Rob