Congrats on your upcoming 5 years! A cruise would be a perfect way to celebrate. With a good planning you'll have a wonderful time! We've cruised several times w/ & w/o a toddler. In fact we just got back from a Sept. cruise on Freedom of the Seas Royal Caribbean. Last year we went on a Carnival cruise. Both times we traveled w/ my toddler son.
For family travel w/ a toddler - I highly recommend the Carnival cruise lines over Royal Caribbean. Camp Carnival was fantastic! You drop off your toddler whenever you want during their open hours. They will change diapers, provide snacks, crafts, activities, there's even a mascot "Fun Ship Freddie" that the kids love to interact with. They provide you with a walkie-talkie in case they need to get in contact w/ you. They stay open very late into the night so you & hubbie can get in a late date night. It was wonderful and my son (3 at the time loved it). He begged to go to Camp Carnival as soon as woke up in the mornings. They treated the kids better and took time to soothe the kids that were crying or were scared. It was also very secure. The kids wore name tags and you had to sign them in & out when ever you dropped them off or picked them up. Overall a wonderful experience. My husband & I were able to really enjoy a romantic vacation and had a lot of time alone.
Now for the Royal Caribbean. We had our son, now 4 in the Aquanauts program; or as my hubbie & call it the AquaNazi program. They were awful. 3 strikes & you're child is out if they have a potty accident. No snacks or drinks, they didn't soothe the crying kids at all. And worse - no walkie-talkie provided. My son didn't enjoy it at all. I spent most of the cruise either w/ my son or worrying about my son. So I didn't get a relaxing vacation and it was very "romantic" either.
Now you will have a 2 year old, so your son would be enrolled in the "Royal Tots" on Royal Caribbean. It's like a 45 minute mommy & me class. You MUST be w/ your child since they don't offer a drop off class for kids under 3.
Basically, you & hubbie need to determine what kind of experience you want for your son. Has your son been in a pre-school or a daycare where he feels comfortable & confident on his own? If yes, the I highly recommend Carnival's Camp Carnival so you can drop him off and enjoy your anniversary w/ your husband. Is he not yet ready to be left alone in a day care setting or would you prefer to spend all your vacation time w/ him? Then Royal Caribbean's Royal Tots would work for you.
As far as food is concerned there is so much food on board that you'll have no problem getting a waiter either in main dining room or the buffet to get what ever kid friendly meal you need, including milk at ANY time. There is also free room service too!! The previous poster mentioned no swim diaper in pools - it's true. There are kiddie pools. Just put a plastic liner over the diaper or get big swim trucks to hide the diaper. Nobody will check or ask.
If you can, spend the extra money to get a balcony room. We always get a balcony suite. Suite rooms have a bath tub, otherwise a regular room has a very small coffin like shower. The baths & showers have adjustable hand held shower heads so you can give your toddler a shower - but it's just hard to do in those tiny showers & you get all wet!
Good luck to you! Feel free to contact me if you want more info, have questions or want to see photos etc. Just plan well and take along treats & toys for your tot's plane ride and pack sand toys for the beach visits! :)
PS. Sorry this post was soooo long!!