It is a common misconception on these forums that somehow campground wifi is somehow insecure and should be avoided for sensitive business such as banking. The truth is that any banking or credit card site and even Google use HTTPS encryption which makes your connection with the site secure regardless of whether or not the wifi, itself, is secure. Your security is ensured by the connection to the site. The horror stories that people cite as evidence to the contrary almost all deal with people who have been fooled into connecting to wifi networks that pretended to be the wifi belonging to the store or airport, etc. If you are connected to the legitimate wifi for the park you are staying at, this will not be a problem.