We have visited several Iberostar resorts in Mexico and have throughly enjoyed them. We don't have kids, but I do know they have extensive activities for kids of all ages. They have an abundance of price points too...you can go pretty cheap or rock it out like a rock star.
We like cruises and have been on a few, but this past summer, went to our first land based all-inclusive, and it was an Iberostar in Mexico. Have to admit, went in with pretty low expectations, but everything went really well. We had an extended family group with an age range of pre teens - 80's.
Food was not gourmet, but decent and enough variety of restaurants to not get bored over the course of a week. Pool(s) were great, and it was really nice that it is truly "all-inclusive". If the kids wanted a smoothie, or the adults wanted an adult beverage - no problem, have two or three. On a cruise, those drinks can really add up. Tips, etc were also included. We did not even leave the grounds. For more than a week, probably would have gotten old, but for a week, great time. Overall, we would definitely do it again.
DW and I did sit through the time share presentation as DW wanted the two spa treatments. Somewhat painful, but happy wife = happy life.
Cruises have some advantages, land based all inclusives have some advantages. I would be happy with either.
But, as the poster below notes, spring break time will most likely be quite busy, so keep that in mind.