Maggie,
As long as the bag is hardsided, you should be fine. I always use hardsided luggage, even though it's heavier, for the extra protection. The only thing I'll put in softsided is clothing only, and even then you risk getting something spilled on it as mentioned above. I was at a meeting once with a lady who had absolutely everything in her softsided bag ruined by some unknown substance. She had to go buy clothing to wear (and she was one of the speakers).
You wouldn't believe the damage my luggage has received through the years. For some reason, Orlando has been the worst culprit. It's like they take my "indestructible" Samsonite bag into a big vise and twist it somehow.
Delta repaired one bag so many times that I finally retired it. They never got it quite right the last time and I was always afraid it would pop open. Not so bad when you could lock your luggage, but after they prohibited that, I stopped using it. I've haven't tried the new security approved locks yet.
Speaking of coolers, we bought a terrific soft-sided one last year from Kohls. It folds fairly flat, so we have put it in a suitcase. We have also used it as a carry-on loaded with food and drinks (it has a retractable handle just like a regular carry-on wheelie bag). We use it during the trip, then fill it with dirty clothes or other soft stuff and check it on the way home. It doesn't keep t hings cold more than a day or so, but would be fine when flying and in a hotel as long as you iced it down once or twice a day.
Sheila