Oh boy! Restaurant suggestions are tricky, because I don’t know your price comfort level, but if you’re talking IN the city, you might have to pay a little bit more.
In terms of churches: St. Patrick’s, old St. Mary’s, and St. Peter’s are all within the city that I can specifically remember as being beautiful churches (I live in the suburbs, so I know my own diocese better). There’s also the National Shrine of the Immaculate Conception, which is located practically on Catholic U’s campus (just off the Red Line).
Evening activities: the Kennedy Center has free concerts and events every night through the Millennium Stage.
kennedy-center.org/programs/millennium/schedule.html
There are TONS of free things to do in the city if you know where to look. The Smithsonian museums have extended hours on certain days:
si.edu/Visit/Hours#ExtendedHours and sometimes host events that are free or for a small charge in the evenings as well. Not sure what your interests are, but there’s that.
And in terms of hotels: you’ll probably be better off price and safety wise if you stay in the suburbs near a metro station. I’d check for hotels near the Orange line stops from Rosslyn to Ballston or the Blue/Yellow line stops of Pentagon City, Crystal City, King St - Old Town, and Franconia/Springfield.
wmata.com/rail/maps/map.cfm?
Just keep in mind, if you’re using metro, it closes at midnight Sun-Thu and 3 am Fri and Sat (and they’re not kidding. I showed up at a metro station at 12:05 and it was shut and locked. Whoops).
Hope that helps enough to get you started!