conjugal camp sleeping

Hi all, my partner and I have decided to go back to car and tent foro our camping in the forseable future, for various reasons. Last weekend we had a test run with our new set up but struck problems in the bedroom department. Our old trusty Colemen air bed developed a bad case of the sags during the night.We bought a replacement (oztrail) mattress the following day. This apparently has a 'two stage' inflation system. We couldnt seem to get our coleman air pump to inflate it very firmly. Perhaps there is a trick we don't know. Or perhaps we need an 'oztrail' pump. Any ideas? Anyway we thought that by putting the two semifirm mattresses together we would get away with it. Unfortunately our air mattress ensemble became a giant bouncy castle during the night. If either of us got up off the mattress the other person dissappeard into an airbed crevasse!. Getting back onto the bed resulted in the incumbant sleeper being catapulted to the tent ceiling. There were a few hysterically funny moments but not a lot of sleep. We heard numerous neighbouring campers repeatedly blowing up their air beds during the weekend. There was also a lot of conversation about failing airbeds in camp kitchen.
So is there a better answer to the air mattress? We have camp stretchers but they are designed for 'solitary' sleeping. We used to have a semi self inflating mattress but would find this too bulky for our current setup. Is it just that we need to find a better way to inflate the Oztrail? Will a foam underlay make a difference? Open to suggestions- thanks, doc.