Darling, I would say just go with the flow, wherever passion brings you I personally enjoy slowy undressing a man while kissing and tasting each other. If you where with me, you would be naked before you get to the bathroom door.

Personally the "nothing but a towel" visual that is now dancing in my head is more than alright with me

Sorry to butt in on the ladies' responses. But neither scenario you described keeps your wallet secure.  

Maybe you locked it in the glove compartment before you came in. That would work.  

But if you're still carrying it and you volunteer to shower, do the disrobing in the bathroom. After showering, walk out nude with your outer garments folded or on a hanger. Lay the clothes gracefully on a chair. With the distraction of you naked (ha!), she'll hardly notice the clothing trick.

The idea here is to protect you, in the shower, from a sudden feeling of insecurity about your wallet. Not that a lady would ever peek into a hobbyist's wallet while he's in the shower!

Your time, your dime, put your shit anyplace you want to put it & do anything you want to do.
Whatever you want to do trumps any weird ritual expectations a provider has.

The funniest thing though is when someone goes off to shower and comes back out damp but re-dressed.  
Do it however you want to do it, but don't be modest on my account .