we don't split cases, but i have a change of clothes for each of us in the carry on bag, plus underwear, plus a pair of shorts for each, plus the swimsuits......that sounds like a lot, but it doesn't take up much room at all....
on our last trip, no one on the plane got ANY of their luggage, because they couldn't open the cargo door of the plane (a 747-400)!!!
This was in Kennedy Airport in New York. They told everyone to continue on to where they were going and the luggage would (eventually) follow. Since we'd already missed our connecting flight to Orlando (in the 2 hours we all stood around the carousel waiting for the luggage to come out), the airline whisked us over to La Guardia airport to catch the last flight to Orlando.
The luggage only arrived at our hotel (the WL) late the following afternoon, but that didn't stop us. We had everything we needed for the first day in Orlando (light clothing, swimsuit, etc.).