CHEBJO said:
We usually drive and I allow each or our two kids to take a backpack with toys of their choice. Once there they usually do not pick up those toys anymore. There is just so much stimulation and new things to do and see that they are more than occupied with the surroundings. Good Luck. (our kids are 3 &5)
At 2 & 4, I think your kids are old enough to either carry or drag their own kid-sized backpacks through the airport, JMO. Of course, that assumes they'll cart their own rather than using you as a pack mule!

But I like the idea of "here's your backpack, choose the toys you want to pack in it." Parental assistance as necessary.
I'm a fan of inflatable toys. DS5 absolutely LOVES beach balls because they are the only balls we let him have inside! They travel really compactly, too.
I also think it depends on how much down time you are planning to have. Our first trip DS was 4 and we didn't have much down time in our five days. Naptime each day was it--we burned the candle at both ends, so we didn't leave much time for relaxing at the resort. Our normally sleep-resistant son fell into bed each night with Pal Mickey and his Stitch light-chaser (say what you want, but it was well worth our $15 investment!!) and conked out immediately.
The only toys we wished we had brought were a few bath toys. DS wasn't particularly impressed with me drawing faces on styrofoam cups and convincing him those were bath toys. . .

In retrospect, a tube of tiny plastic animals would have gone a long way!
Good luck!