It depends on what kind of vacation you want. Sounds like you are wanting a beach type of vacation. DH and I have been to the Club Med at Cancun twice and LOVE IT! It used to be for adults only but I recently got a brochure saying that they have turned it into a family destination. They also have a few other family destinations across the globe (I heard rave reviews about the Turks/Caicos one). We live in Poway so it's still two plane rides to get there, but they are short rides. We are planning to take our two kids there in a couple of years for our 10 year anniversary.
Another cool place to go that is very family friendly would be Rapid City, South Dakota. Definitely not a beach resort, but they have a bunch of little cabins along the stream/lake, lots of open space for kids to run around (we love Lake Park), and lot of cool free or inexpensive kid friendly things to do (Reptile Gardens, Story Book Island, Dinosaur Park, Mt. Rushmore, Crazy Horse Monument, Bear Country...oh the list goes on and on!). We just took both our kids (age 3 and 1) there in early May to visit the in-laws. We stayed at Lake Park Campground in a 2 bedroom cabin for $75 a night. We were 1/4 of a mile away from Lake Park where they have 4 very nice playstructure areas for the kids to play, ducks to feed, and a nice walking trail/path. My 3 yo son LOVED having so much open space to just run and run and run! And my 1 yo daughter had fun crawling all over the park on the grass. And don't forget all the cool things to do in the Black Hills (like driving through wild buffalo and the casinos). Plus a lot of the hotels in Rapid have kid friendly play areas or even indoor waterparks. It was really a fun and mostly relaxing trip for us.
Good Luck!