Hi there! Thanks for starting the thread! I'm a longtime DIS reader but finally set up a profile.
We've done three cruises: once when I was pregnant, once with our son when he was 16 months old, another when he was newly 3 years old. This time around, he's 6 and his sister is 2 (her first cruise). We do WDW pretty regularly, too (we love it but have to admit
DCL is more relaxing--a vacation rather than a trip).
The first tips that come to mind are bringing a stroller on boarding day, booking nursery times ahead of time (if desired), and being sure to visit the kids' club during open house.
It's easy to hesitate on the stroller since you may not need one much at this point, depending on your kids' exact ages, or maybe you only need it for the younger kid. I recommend having one even if you don't normally need it because there can be a decent amount of waiting / needing to be contained. A sit-n-stand type stroller can be great if your older kid isn't wild about being in a stroller (and isn't as big as a traditional double stroller). And you can fold it and stow it under the bed in the stateroom, potentially not needing again until the last day.
If you are interested in your kid(s) using the nursery, it's a good idea to book a few times ahead of time. In my experience, it's never been wildly busy / completely unavailable, but it brings peace of mind (and this is a spring break cruise, so I'd anticipate it being busier than the off-season cruises we've taken in the past).
Also, we didn't know what the open house times in the kids' clubs were when my son was 16 months old and would've skipped them if someone hadn't explained them to us. The kids' clubs are intended for ages 3 and up (if fully potty trained), but during open houses, toddlers can explore with parents. It's wonderful! Be sure to check out when the open house times are during the cruise so you can enjoy the play areas as a family.
Let me know if you have any specific questions and I'd be happy to see if I can help.