Home canning using plastic containers
Use glass.
Honestly never heard of canning using plastic containers. The container may go soft and lose its seal and make a mess. Go with glass!
Use glass and make sure you use recipes with a final pH of <4.6, your boiling method is insufficient to eliminate botulinum spores and items like Stew with mixed ingredients pose a risk.
USDA has canning recipes including time/temp combinations and verified pH to help you follow a safe recipe. http://nchfp.uga.edu...tions_usda.html
Recommended resources for home canning safely: USDA Guide to Home Canning (linked above), Ball Blue Book, or So Easy to Preserve (Cooperative Extension: The University of Georgia)
I agree with everyone who says to use glass. You can buy the Ball glass mason jars at many "big box" stores, at least around me you can.
Depending on the food type, you could can using the hot water bath method or pressure canner method. In general, you can jams, pickles or other acidic foods with the boiling water method, and any soups or animal meat should only be canned using the pressure canner method. Check the USDA website FurFarmandFork mentioned above to help decide which method is best.
I would make the stew as usual and pack it in a cooler with ice. Much simpler than canning.
Why bother trying to can it if you're not storing it for long periods of time? Like Sqflady said, just cook it before hand, keep it in a normal tupperware and store it on ice in a cooler. Since you're car camping it shouldn't be a problem to transport and you're already planning on reheating it.
The real benefit to canning is being able to store your food for long periods of time at room temperature. If you don't need to do that then just treat the stew like leftovers.
cook and chill, don't can......the likely hood of getting it wrong when canning with meat is very high!!! Don't spoil a vacation with botulism!