You could do that, but my advice would be to pick a cruise and cruise line that have an itinerary you'd like. The transportation issues are generally quite similar. From Disney World, its about an hour to Port Canaveral. Tampa isn't that much farther (maybe 15-30 minutes). The transportation issues are the same, except if going on a
Disney cruise there's always the option of obtaining Disney transportation and if renting a car, there are rental agencies near the port.