As someone who goes to both WDW/DLR- this my must do DLR list if I only had one day and was focusing only on things that are different from WDW:
CA -in order of importance to me:
Radiator Springs Racers- single rider line
Soarin only if the California version is running
Guardians
Monsters Inc. Ride
Incredicoaster- single rider line
Luigi's Rollikin' Roadsters
Web slingers
RSR/Soarin (California version only)/ Guardians (if I liked TOT like you) and Monsters Inc. would be the 4 absolute musts for me. The others would be ones I would want to do- but would be my second tier priority.
If I wanted a sit down break- I would head to the Animation Academy and draw a character and if I had time for a night time event or show it would be WOC or the WOC dessert party. If you get a chance-- see Carsland at night-- if you enter through the Pacific Wharf area- the view is breathtaking.
DL:
Alice in Wonderland
POTC (so much better at DLR)
Space Mountain (so much better at DLR)
The castle Walk through
Haunted Mansion (hatbox ghost- need I say more)
Small World
Indiana Jones (if open)--- I hate Dinosaur and I love Indiana Jones
Disneyland Railroad (specifically the part that runs from Fantasyland back around to Main Street)
Nemo (nostalgia for the 20,000 Leagues ride)
Toad
Snow White
Pinnochio
If you are there at rope drop-- you can probably knock out all the Fantasyland area rides pretty quickly.
Alice/POTC/SM would be my 3 absolute musts.
And yes-- I know Matterhorn isn't on my list. Every few years we say hey we haven't ridden that in a while-- we should go do it- and every time we get off and say- oh yeah that is why we don't ride it, we are good for a few years now. It is a rough coaster.
As far as food, my must have would be to get a churro at the cart by the castle. No churro at WDW remotely even compares to the DL castle cart churro.
Outside of that, in our opinion the CS at DLR is much better than the CS at WDW--- I'm sure because of the local crowd. Just look at the menus on line and see what appeals to you ---- If you are a Marvel fan, you might just want to go to a cart and try the schawarma. Cars fan? Flo's is pretty good and some tables have a great view of RSR. Beauty and the Beast fan? The Red Rose Tavern does have the Grey stuff. There are a ton of CS options.