So we've now done Disney twice as parents, once with a 2.5 year old and once with 5 year old and a 22 month old. The first trip with the 2.5 year old was so relaxing. Kiddo was so entertained, did well in the stroller, napped on the go. Zero issues. When we went back it was a whole different story - the younger one HATED the stroller (screaming, physically flat out refusing it EVERY SINGLE TIME), refused to walk where we needed to walk, didn't sleep well at all. It was honestly a little bit of a nightmare.
We haven't done a cruise with them, but we have done beach vacations and same deal. There've been good ones and bad ones. Times where they were easily amused and happy and we were all relaxed, and times where everything went wrong and we were stressed and miserable.
Point being, it's a toss up. Choose whichever you think will make you the happiest, and know that there's no right or wrong here because no matter which choice you make, it really all depends on your kids and the phases they're in at that time. It's hard to plan for that or to know exactly how it will all pan out.
I've always found that being in the parks takes the pressure of us as the parents to entertain them, which is in and of itself a relaxing break for us. That said, I have heard that the kids clubs on
Disney cruise lines are amazing, so that might be a factor for you in terms of getting some kid-free down time.