Hurl obscenities at the f*cking trams on Princes Street.
Go here for a top notch breakfast - the one on Elm Row
http://www.valvonacrolla.co.uk/
The National Museum is very good, and free, as is the Museum of Modern Art, which is a little bit out of the city centre but worth the trip.
The Castle is good but it's a rip-off.
If they are football fans, Hibs are at home on Saturday, Hearts (against Ayrshire's finest, Killie) on the Sunday.
A wee trip out to Cramond Island could be good, warn them to check the tides carefully!
Leith is nice for a stroll round as well - there are excellent chippies.