Perhaps they lay on the couch and watch a movie in their pajamas. Perhaps they take a nap together. Perhaps they cook some pancakes, or talk about their troubles. Perhaps they cry, perhaps they laugh...
it's a Peanut Day, they can do whatever they want as long as they do it together!
"i don't know if we can do a PEANUT day... i have to run some errands with the madre."
"oh... well we could maybe have a mostly peanut day..."
"sounds good lovey."