Is this going to be a permanent bedding solution or just a camping thing? I have a Coleman Queen-sized one that isn't too bad. I do NOT recommend sleeping on them nightly though. They are like wild mushrooms, they are good to an extent then they'll make you sick!
If you both are planning on sleeping on it, I would recommend the double sized one because towards the edges of these blow up beds, they do tend to lose their sturdyness. Sleep close to the center of the bed and you'll be fine! If you buy two singles and push them together, one of you will end up on the floor/ground in between the two before morning.
...and on that day when my strength is failing, the end draws near and my times has come, still my soul will sing Your praise unending, ten thousand years and then forevermore!