Be careful on the printer, make sure you get one with cheap cartridges, being 5 he's gonna like to print shiny colourful things. Avoid Lexmark printers like the plague.
Yeah it doesn't need to be too hi-spec.
Seen this:
http://www.currys.co.uk/gbuk/hp-pavilion-s5545uk-p-desktop-pc-with-monitor-printer-06318515-pdt.html