Where do you go when you have to go?

I know funny title.  And we are not actually talking about Jesse and myself, we are talking about Bella.  This is a conversation we have quite often when discussing the obstacles we will face as she gets older and bigger.  Right now she barely fits on changing tables, although she has probably exceeded the weight limit.  But what do we do when she gets even bigger?  Where do you change a 50 pound child who still has to wear a diaper?  It's one of those things we bring up, but don't really want to think about.  So I hope and pray that some day she will be able to sit up on her own, at least then we might be able to manage a little easier than someone who has to lay down flat.  But for now we cross our fingers that while we are out and about, she won't have a dirty diaper.  Of course it seems to happen more than not, and then we are on the lookout for someplace to change her.
I also wonder what they do in school. I imagine at this point they have a changer in the restroom that they use. But again as Bella gets bigger, I'm not quite sure how they will manage either.

I have in the back of my mind an idea to make some sort of large mat that can be laid on the ground, but just thinking about laying something on the ground in a public restroom grosses me out.  Of course it would be washed any time it was used, but it still means being on the ground.
I don't really have a good way to wrap up this topic.  I guess we will just see what happens as we get there.