We took our barely 3-yo son on our 1st
Disney cruise this past Nov and LOVED, LOVED, LOVED it! Our son couldn't be more entertained nor happier. Our son, too, had cried when we're trying to get him out of the club. He STILL talks about going back on the Mickey Mouse Cruise Ship!
RE: the club for 2 yo. It's all based on potty training. If your 2 yo is potty trained, they'll let him do a "trial run" to see if he is potty trained. If not, you are definitely welcomed to stay and play with him in the Club. If you're looking for some alone time sans kids, you can always sign him up for the nursery, but be sure to book that early as it does fill up quickly.
BTW - the great thing about going in May is the weather is generally nice and warm, so you'll be able to disembark and enjoy the ports or stay on the ship and splash at the pool. Your young ones will NOT lack for entertainment.
As for the adults, it does depend on what you're looking for. I've heard mixed reviews. My hubby and I enjoy working out, going for walks and laying out by the pool and are early birds (to bed and rise), so we didn't need much to keep us happy. If you're looking for constant adult entertainment, you may want to check a recent Navigator which shows all the activities available and decide for yourself.
But, all in all, we had a fantastic time and couldn't be happier with our decision to go. In fact, we're booked for this November already if that tells you anything.
Good luck ... and have fun on your cruise if you do go!