Can I charge/maintain 12V batteries in parallel?

"For while camping, I bought 2x40W Coleman solar panels (80W total.)"

Two forty watt solar panels will keep your batteries charged during storage but they won't be sufficient to recharge your batteries when camping during normal use. I'd try to return them and restart research regarding solar systems. If your two batteries are group 24s with 90 amps or so each you'll need 200 watts of solar minimum.