I hunt a lot of ducks here in CO. 2 3/4 is ok, but if you have the means to get a new gun that handles 3" or 3 1/2" I'd do that. You definitely want 3.5" for geese if you get invited to go.
Ducks are fast, move like crazy and can be difficult to hit even from blinds. while I've killed plenty with the cheap Winchester steel shot from Wally World, I love Remington hypersonic. I've taken some birds pretty far out that just weren't going to commit and kept buzzing by or flaring off.
The biggest reason I recommend the increased shell size is if you get wounded birds on the water trying to swim away, those extra pellets make a big difference. Just don't shoot while the dog is out retrieving!!!

As far as eating, teal can be delicious, just got a bunch for the early teal season and enjoyed some teal breast and home garden jalapeños wrapped in bacon. Delicious!

Now the bigger ducks take a lot more prep work. Luckily for me I get plenty of big game meat, so I save all my duck and geese breasts for the year then take them all in to Hudson meats and get them processed into snack sticks and various custom products which eliminates any tastes you might be worried about and makes them quite tasty!


Also, I'm sure you've read the regs, but just make sure you have your HIP numbers, as well as Colorado and Federal waterfowl stamps. You might get into some trouble if you get stopped without those!