If your staying at the same park you say is lousy Probably not. Was it lousy because you couldn't see or connect to the wifi because it was too far away? Did it work well in the office? If it was then the Booster will pick it up and boost it to the inside of your RV. some even provide a unique in RV private password protected wifi using the parks wifi or a cell network ( the 4g model you described ).Probably More likely and as we have found the park WiFi is not able to sustain 20-100 or more people on the same connection. Invite 50 of your friends to all log onto your home wifi at the same time and see what happens. They all get a strong signal but the pipe is just too small.
If your staying in one place do they have phone service at the site ? can you get internet via that? If not Bite the bullet and get a Cellular Wifi that works well where you are staying. You say in didn't work that well .. maybe your carrier isn't the best in that area.