We used a honeymoon registry when we got married. It wasn’t for a Disney trip, but the site we used had every destination imaginable. My tips:
-people liked picking out actually activities to buy us. The site had options like contribute to airfare, partial hotel payments, I would assume partial cruise payments. This seemed a little tacky to me (since it was basically saying throw in some money to buy my plane ticket). I felt much better about picking activities and experiences like massages, excursions, dinner at a specific restaurant, snorkel rentals. The nice thing is that our site just sent us the money for it and you didn’t actually have to book the massage/excursion/etc. People really liked the idea they were gifting you a bike ride, but if it turned out you were sunburned by day 5 and didn’t want to ride a bike, you could use the money towards your hotel bill.
-make it sound fun. We could add little comments on the different things so we said stuff like we really want to find a treasure chest of pirate booty: snorkeling gear for 2. Our guests LOVED writing little comments in the cards like “finding each other was treasure enough, but pirate gold never hurt”. It just made it a lot more personal than throwing cash at you.
-our site would send us an email every time someone bought something. This really ruined the surprise of our shower. If I had it to do over I would set up an email filter that sent the messages to a folder I didn’t check.
-speaking of the shower, it was a little odd for my family that there weren’t big gifts to unwrap and ohh and ahh over. It was a bunch of cards where people wrote “I got you the massage” or printed out the order sheet. I made sure to yell out what each thing was and to make a big deal about OHH Aunt Diane got me the horse back excursion. I can’t wait! Just to make it a little more festive since at our showers people usually hold up whatever and everyone says ohhh those are the nicest pans/towels/pencil holders.
-just like a store registry have stuff at different price points. I did this by hedging a few of the costs. I knew that one excursion was $125, but I put down it was $75, etc to give people more options. Like I said earlier the site just sent us the money in the end and we paid the difference. We tried to have lots of variety from picnic lunches to more expensive activities so everyone could find stuff in their range.
For us it was the best thing ever. We were both already living on our own and we already were struggling with combining 2 complete households. The last thing we needed were more dishes or kitchen appliances. For my family and friends almost everyone loved it- one older family grumbled that all young people want is gift cards these days, but everyone else thought it was fun and practical.