You should take this challenge: If she says no to flip flops, go barefoot instead, than she will allow flip flops :-)
Strip Soccer (penalty shootout)
-> me and 3 male friends (so we were 4 guys), got drunk and went to the pitch nearby. Every time you missed a shot, 1 article came off. We played until 1 was completely naked. He had to walk home naked.
Strip Mario Kart
-> This was mixed genders. Every time, you came in lower than 3rd place, you had to strip 1 article. If you came in on last place, 2 articles. It was fun, because 3 guys and 1 girl ended up naked.
I had sleepovers often, when i was younger, especially with this one friend and his younger bro. we practically were together more often than i and my parents. We also slept naked, sometimes in his bed, sometimes i slept on the floor on a matrass.
Very extendet and detailed, very good. i answered as male in his 30s who has 3 sons and 1 wonderful wife. We talked about this topic alot, also with the boys, they could need some of this i think.