I actually have some bunk beds for sale. They are nice, but the ladder is built in. We have an almost 2-year-old climber, so we need to be able to take the ladder down. (You may have the same problem.) Also, when you climb up the ladder, you have to climb over the foot of the top bed. Our six-year-old could do it easily, but we weren't sure about our younger ones. Email me privately if you are interested! I will give you all the details. ____@____.com
I have never heard of wooden bunk beds breaking. However, a friend's metal bunk beds started to bend after her children had clibed up and down them for several years. I would definitely prefer wood.
Hope this helps!