Hello willmouse, I've had chickens almost all my life so can hopefully answer some of your questions.
Chickens do turn your lawn over quite a bit - they scratch when looking for grubs etc. so it'd be sensible to just get a couple if you're going to keep them in a smallish garden.
The chicken house doesn't need to be in the sun - as long as the house is nice and draught-free but well ventilated and spacious, it doesn't matter where you put it.
If you get a breed that isn't flighty (e.g. silkies) you don't need to worry about them going off. If you get one that can fly you will need to clip their wings - it's easy and no different from cutting a child's fingernails. You can find instructions on that online. Having said that, my chickens can get out of their run easily but they tend to stay in there, but we've also had some before that were terribly keen on going into the neighbours' garden.
I think you should let them out every day, and yes, they do poo - but they won't hang out on the climbing frame. It might be a nuisance to clean poo off the patio though.
I've never had a problem finding someone to look after them - they don't need much really.
If you get hens then you won't have any problems getting pecked. Mine are all very friendly and used to being picked up by the children - they patiently stand still now when a child approaches! Our current cockerel is very nice too, but we also had a viscous beast once.
They don't smell as long as you clean their house out regularly, and hens are not noisy.