Have you got cats/dogs in the house?
Otherwise I'd recommend building a C&C cage from grids, so you are flexible as to the layout and design and can devide if necessary or go two storey. It's sheaper than a conventional 2x5 ft cage, which would be the recommended
minimum by the RSPCA for three boys.
For inspiration look here (start from the end) or have a browse through the housing section.
http://www.theguineapigforum.co.uk/showthread.php?t=142&page=29
For three boys, ideally, you want three of each - bowls, hides, water bottles etc. They are very much at an age where they are still gamboling through everything right now! Water bottles will take time to take to, so feed them a little bit more watery veg to make sure that they get the necessary fluid - there is a lot of fluid in most veg, so you need not be worried. You can put water bowls out, but be prepared to change them twice daily, as what you boys are doing to it is pretty normal!
You can littler train them to a degree. Best put any tray under the hay rack, as piggies like to munch when on the toilet; but success is rather limited with most. Poops go pretty much everywhere! Some piggies are tidier than others.
Make sure that you introduce new veg slowly and only one at a time, so you do not cause any tummy upsets. If they don't like something, leave it for a while, so they can get used to the smell and texture and then serve it some time later again and again... The more variety the learn to eat when young, the less fussy they will become.
Here is a link for a good diet:
http://www.theguineapigforum.co.uk/showthread.php?t=37030
There are more informative threads for piggy newbies in the
reference section.
For general information, Petper Gurney's online ABC is a very good source of information - he was THE authority on guinea pigs.
http://web.onetel.net.uk/~petergurney/atozmainpage.htm
