When I used to do proper camping (non-site), I just used to find a suitable rock/dune/bust/object to hide behind! Being male, that was only necessary for no2's!
On sites it is easy to use their toilets.
Personally I would not bother. Personally I find these type items more hassle that they are worth.
As for showering, if you are in the wild the only person that will be doing wildlife watch will be you.
If you are worried shower in trunks.
Personally I like showering in the wild!!!
Just my thoughts on the subject.