Big Boy Bed Dilema

I've been putting off moving Warren into a big boy bed since he hasn't tried to climb out of his crib yet (surprisingly). But my mom and I took him furniture shopping the other day and he seemed pretty excited to try one out. Unfortunately, I had no idea how expensive beds and mattress were! So John brought home a set of bunk beds from Ocean Pond. They are actually old military bunk beds (yes, Ocean Pond has alot of history out there:) They are still in pretty good condition, I just need to sand and paint them - which I enjoy doing projects like that, so bring it on! But the down side is that since they are military beds, they are not standard size. A twin bed is 39x75, these are only 30x75. So of course no local places carry these types of mattresses. I found a place online that carries them and will ship to our house, but I can't bring myself to order them. Reason being - apparently military beds are also the same size as prison beds!! The place online is for "prison mattresses"!! I just keep seeing myself trying to explain to our UPS guy why he's delivering prison mattresses to my house!
So I think I'll still fix the bunk beds up, but just take them back out to Ocean Pond for when the guys stay out there. For now, we converted Warren's crib into a daybed (which was just removing the front piece off). Tonight is his first night sleeping in it this way and so far so good. He hasn't tried to get out of it once, nor has he falling off:)