I've been ordering cheap 2nd hand DVDs of films for me & my DD to watch for years - it's a great way to have a 'movie' night on the cheap. I usually get some nibbles & we snuggle up under a blanket for our chosen film. You could make it a bit more fun by making tickets to buy, setting up a stall for popcorn, maybe get a wee daft hat & torch, switch lights off (assuming your DC isn't afraid of the dark) & show them to their seat etc.
Plectrum I'm loving the idea of lights off and showing them to their seats! Normally I just 'make' popcorn for movie nights for DC aged 4 and 7 but I'm so going to show them to their seats with a torch in future!
We have 'movie and pizza' nights every Sunday. DD gets to pick the movie, I make pizza from scratch (easy once you know how) and we eat from our laps on front of the telly, which is normally forbidden! It's her favourite night :-)