Thanks for all the suggestions and ideas on diapering Wesley at night! I think tonight we'll try putting on a pair of training pants' underwear (the padded kind that pull on) under his diaper. I think that although it will keep him wetter than a diaper would, it may be enough to 'seal' or absorb around the tight parts of his diaper area enough to keep him from leaking. In theory anyway. I have a few pair from when Kristopher potty trained and I have a few we had for Brianna (and I'm pretty sure he doesn't mind wearing pink undies to bed) so we'll start there since it's already here. And I'll try one of Lynae's size 3 Luv's on him over that (I think that was suggested over on FB in comments there).
Thanks for all of the ideas, and I may be back soon with more questions!
As far as 'bagging' his pee during casting, I will definitely ask about that. (By bagging I do not mean catheterizing, but rather catching the pee once it's out rather than having it all go all over in the diaper). That sounds like it may be necessary to keep the cast clean since we wouldn't be able to use a padded underwear with the cast.