They occasionally come up to do dishes but otherwise have the means to do all of their cooking in their own space and they have their own dishes, pots and pans, etc. 

Don't block any windows but you could put, moving from doorway outwards - maybe a tall thin hedging evergreen on each side of door (could be in large pots), maybe some day lilies against the wall under the windows fronted by ground cover azaleas, climbing vines between the windows, a low growing (3') shrub with variegated foliage under the smaller windows and something like a pampas grass or butterfly bush at opposite ends of the building.  

I've thought of replacing the old cracked sink   with this console sink Last time we had got body sprays and shower bench installed for no reason that no one ever used.

For the kitchen drain, you should pour a pot of boiling water down every couple of months to prevent grease buildup.If your problems have been ongoing, it may be a good idea to have them run a camera through the line to actually see what the issues are.

TWICE, I have found a bag of pot and Ive found pot pipes and pornographic videos and magazines there.

You just have to get out there and play.You'll never learn the game sitting on the bench.

There’s no other pot of gold to hold out for.

@Jarrod Gregory we called it the honey pot.

So far we've taken all the wood off the top (underside) of the porch and replaced it with tongue and grove pine and replaced the single ugly exterior light with 3 brushed steel pot lights attached to a dimmer.

Can you find a pot of gold at the end of the rainbow?