I don't have suitcase specific ideas, but definitely something that rolls, and make sure you don't exceed the weight limit for checked baggage.
But I will recommend packing cubes. They are fantastic for organizing things within luggage. I use them when we travel, one or two for each child, then for the grownups (bigger clothes) one for pants and one for shirts each plus smaller ones for socks and underwear. With the kids stuff I roll an outfit together before packing as well, so it's easy to pull one days worth of clothes out.
When we travel we just use carryons. If we need to travel light, we'll used 2-3 carry on rollerbags. If we have more room, we each have a carryon size bag (my boys, 9 and 6 have rolling duffels, my daughter, 4, has a rolling suitcase and my husband and I each have a rolling suitcase - all carry on size). Then we each wear a back pack for personal things, like books, toys, etc.