Portable Heater Recommendations? (CO Detector Issues?)

Hi everyone- Haven't been on the forums much lately because we've been CAMPING! :D I have a question though- a couple weeks ago we were camping and it was really cold, so we had our camper heat running. The carbon monoxide detector went off in the middle of the night. We vented everything out and turned off the heater just to be safe, and the detector didn't go off anymore that night. I don't know if it was a false alarm or what (it's also the propane detector, but we couldn't smell any propane.) None of us had any symptoms whatsoever of actually breathing too much CO.

We're going camping again this weekend, and it's supposed to get down in the 20s. I'm a little bit nervous because if the heater is causing a carbon monoxide problem, we obviously won't be able to use it! So, I want a portable backup heater just in case. I think the 20s will be too cold without having some sort of heat.

What are your best portable heater recommendations? We have a 3-bed hybrid, so we really need the heat to travel to both ends of the camper if possible. Also, we have two kids, so it needs to be as safe as possible. We will set it on either the dinette or the stove top so it won't be on the floor where they can walk into it, but I'd still rather it not get super hot to the touch.

Also if anyone has any experience with their heaters causing their CO/propane detector to go off, I'd love to hear any suggestions surrounding that as well. I'm really hoping it was just a false alarm though. I think I've read that sometimes other gasses or air particles will make the alarm go off? Thanks!!!