more ideas: clean the house (or apartment, condo, or where ever you live) or part of it
make them "breakfast in bed" or something like that
find some cool free attractions and take them there
(this one will require a bit of money but shouldnt be too much [unless you already have a blank cd]) get a blank cd (i have gotten them at a dollar store before) and make a cd filled with songs that they like and that remind you of them, take a piece of paper (can even be the one that comes with it meant to have the tracklist written on it) and decorate it (you can write the tracklist or do that on a separate piece of paper to give to them after they listen to it so the songs are a surprise the first listen). if you dont have a thing that can "burn" a cd or you dont have a cd player then a spotify (or any music streaming service) playlist will work.
a movie night at home. maybe if you can take them to a store before and let them pick out a snack or two before and you can watch one or a few of their favorite movies.