Outdoor wedding rain scare

Hi all!
My fiancé and I are getting married in two weeks (!). We’re having an outdoor wedding (the ceremony and reception are both outside at someone’s not-big-enough-to-hold-our-guests house). The venue was free and BEAUTIFUL, but there is an 80% chance of thunderstorms in the forecast. I know weather changes all the time, but I’m a little panicked. We thought about renting a tent, but I don’t know if we’ll be able to book one in our small town or if they even have one big enough to house a ceremony and reception for 100 people. The lady whose yard we’re using goes to our church, and she’s super nice. She’s so nice that she offered to rent the church for us, but I really don’t want to do that if it doesn’t even rain.... especially because it’s a Methodist church and they have a TON of rules (like not moving the pulpit and having certain tassels out), plus I don’t like the layout of the actual sanctuary for a wedding. The entire building is outdated, including the bridal suite (we’re talking very ‘70s wallpaper from floor to ceiling). What should we do???