I wouldn't mix chickens with guinea pigs tbh - they eat different things, and the chooks could be quite mean to the piggies!
Chickens are REALLY easy to keep - we have 4, get 3-4 eggs a day which is MORE than enough for 5 of us!
Cleaning out - we clean them out totally about every 2-3 weeks (depending on how wet it has been) - I also scoop out poo from the house in the morning - takes 1 min. If you are clever with what sort of house/run they have then cleaning can be extremely easy - although I don't particularly like the eglu houses, they are very easy to clean - you just hose them down. Some houses have pull out trays that you can use to collect the poo and empty off in the morning.
Easy - extremely!
Going to bed - they see to that, when it gets dusky, then I shut their door to keep them in till a reasonable time!
Perches - yes. Their house should have perches which are the highest point of the house for sleeping on (although 1 of mine never perches, and another isn't keen. They will also need a nest box, which should be the darkest place in the house. For ease with the children it's useful to have an external nest box.
Have a look at my blog which has a few pics of our house and run which dh built - we have an enclosed house/run because we have LOTS of foxes. When we have to replace this flock, I want to build a new house and run more like this to give them a bit more space, and also I want to get a Brahma, which is a BIG chicken!
If you read through the blog, there's a fair bit on setting up in the first place, and the things we found hard.