@Bridget254 Better start calling hotels, and plan to pay for their stay. Insurance isn't going to help you. I am sorry that you are having this issue.
When you have a septic system, plan to have the lines checked and snaked once or twice a year, and to have an emergency plumber ready to show up. What have we found in our lines? Toys. Diapers and incontinence products, both adult sized and child. Massive clumps of so-called biodegradable personal wipes and canned sanitizing wipes. Feminine products. Guests flush everything imaginable.