computer 1) if they are macking drawings for communications and having to do with houses, they are prob using an autocad type program which can be a pretty intense program, memory and cpu wise so focus in those areas for that. he will also need/or want/ or be happy with a good solid video card to see the detail in his drawings, you also need to find out what monitor he wants and what resolution, alot of people who do business drawnings use 22" monitors with higher resolutions to see the detail and be precise.
computer 2) anything will do, for what you mentioned. but whats your budget? and like savage said if he wants to play games your gonna want to get him a good vid card other wise he will complain to his dad and you will lose that customer.
i like hard wire personally. specially if the dad is sending his drawings into work, they can be pretty big in size and there maybe some lag in wireless which he wouldnt like.