This almost matches my kids ages when we cruised and did Disney World. The cruise was MUCH easier (both were fun though). It’s much easier to deal with a baby on a cruise for the reasons others stated- your room is right there, there’s always food nearby, the nursery is great, you aren't standing in lines, and you’re. It out in the heat for the whole day. Keeping a semblance of a schedule is possible on a cruise for a baby too.
The other big advantage with your large age gap is that it also gives the older one some time to do their thing (hang in the Oceaneers Lab, watch a movie during baby’s nap, take a swim with mom or dad). Our older one sometimes gets lost in the chaos of a new baby and having to adjust plans/not do something because of the baby’s schedule or diaper or nap or whatever. On the cruise it was much easier to manage both kids equally and let the older one have more “me” time.