Many thanks for your thoughts everyone - I thought you might like an ideas session.
Thoughts:
Windchimes - def. possibility - slight drawback is that the carport is near the house and we often have the back door open - I know wind chimes make a pleasant sound, but my mother might find the constant sound a little grating.
Car cover - have considered it, but I've heard that sometimes these trap the air and cars don't keep particularly well under them - the nice thing about the open sided carport is that it seems to provide an ideal car keeping environment. A tailored cover may require a big of extra effort to put on and off properly too and the car is regularly used.
Retractable lines - I have got one that I took a look at - the slight hiccup is that we drilled holes into the beams in the roof and the lines pass through these in about 4 places so the washing doesn't sag, so its a bit of an effort for my elderly mum to do (and fiddly for anyone else) - esp. since she fell down and hurt her shoulders.
'Blue Roof' - might be worth some more thought - putting it on a frame might be a little too much effort, but winding around a couple of poles to weight a light tarp. at the ends and unwinding over the car, or weighting a tarp along all the edges by making a fold and filling the seam with something heavy like some big pebbles might be worth considering. That way I get something I could just quickly drape over the car.
Birds and bombs just about sums it up!!
All suggestions most welcome.