Don't try to do everything on your first cruise. Check out the daily navigators, and pick a few activities that your family would really enjoy.
100% agree with the two year old activities. Try to get the 1st diner, otherwise you have to get the kids to eat after 8:00. I would also recommend an inside cabin, that way you and your children can go to sleep at any time of the day. I would also think about the kids clubs for your 4 year old. The kids clubs are amazing, especially since the renovations. Just make sure that at the port, you register your kid for the oceanear club/lab and they will receive a magic band that is used to enter the club. There is a $12 refundable deposit on the magic band. The only downside is that your 4 year old will be playing with 11 year olds. So if you are OK with that, just leave your kid in there and he/she will have a blast. If not, I still would have your kid go in the club, but just for an hour or so. With the adults, Disney provides cool activities for just the adults. So if you wanted to to have your parents watch the kids for a night while you went to the clubs or any of the adult only restaurants. You could also do adult activities with all four and just pay for time at the nursery for your 2 year old.Disney also provide fun activities for families too, just keep mind that some activities do cost extra (even with the adult activities). You could also wait in line to see the Disney princesses (which you have to get a ticket, but it's free) or see characters like mickey, Minnie, Pluto, etc. The waits for the characters are extremely short compared to WDW wait times and the interactions with the characters are so much better on the cruise. The characters also have cool outfits that are unique to the DCL on special nights, like pirates nigh and formal night. Also, it's really easy for you to want to do everything on a cruise, but don't force yourself to do anything. A lot of the activities on the cruise ship will repeat and it's also your vacation. Don't stress out because you didn't do one thing, just relax and do what you feel like doing.Since your two-year-old won't be able to go to secured programming at the clubs or swim in the pools (unless he or she is completely potty trained), take advantage of open house kids' club hours or book some nursery time, use the Nemo's Reef splash zone, and check out some of the activities specifically geared to the younger set like Wake Up with Disney Junior, the Pirates and Princesses dance party, and Toddler Time (see your navigator for times.)
Consider eating at a sit down restaurant for lunch on the first day rather than Cabanas. (Some will disagree with this.) It seemed much less crowded and the food was decent.
Don't feel like you have to go all crazy! Just enjoy what you can! It'll be a blast no matter what! Get a taste and a feel for the cruise and next time to you can try to cross everything off a list!
TIPS:
-Bring your own tervis/mug: main deck floor has soda machine available 24 hrs, its nice to fill up before bed.
-Bring a pillow case or something to get signed by ALL the characters. You drop it off at front desk first day and I think its returned at the end. 2 things per stateroom (or per kid if +)
-Disney allows you to bring your own alcohol!! So monopolize on that and pack some miniatures for those tervis drinks at night
-Room service doesn't cost extra and you can get a cake of the day and or mickey bars which is pretty awesome, although I never have enough room!
-Don't forget to bring door decor!! You can totally decorate your door as long as its magnetic! If you use stickers and it leaves residue you could be charged a clean up fee. But magnets are fun!
You'll see a lot of decorated rooms and FE's (fish extenders, with is kinda a gift/craft exchange) and there's plenty of threads about that! FE might be a bit much with young kids on your first cruise, but I wish I had done it my first few cruises. Took me a while to discover it.
-Also if your into it, don't forget you can get dressed for Pirate Night!! It's such a blast and I usually hit up Target after Halloween and you can usually find some Pirate things on clearance!
Just a few tips!! But you'll have a blast! DCL is the best!!
They no longer do the character sining.