Thanks for the pointers (which I should have read before leaving).
I ended up taking a combination of the routes.
Down Maybury Road pavement (because we were running late and the pavement is the only safe way there) and under the Gateway tunnel
Round the cycle path to the tram stop Toucan (I normally go through the car park but thought I would try the official route)
I then made the mistake of trying to cut onto Lochside View too early and had to cycle up a grass bank beside the Ibis to avoid the stairs.
Up Lochside View and through the (2nd) underpass to GSR.
Pick you the canal to Hermiston House Road and then wait for a gap to cross the A71 and join the campus on Harmiston Walk (sic).
On the return we tried something a little differnt following Hermiston House Road to the end and picking up Gogar Bank before taking GSR down to the "curly" bridge and along the north of the A8.
With the possible exception of crossing the A71 it was all very pleasant on Sunday although I would probably tweak a few bits on a work day. for instance GSR with a loaded tagalong would make me nervous during commute times although perhaps only because I don't ride it regularly.
I would also use Lochside Avenue to access Lochside View next time (Blueth, I don't use the Gyle centre underpass when towing passengers as it requires crossing the potentially busy roundabout at the centre of the car park and brings you out onto the wrong side of Lochside Crescent.)
Gembo, your route would probably be preferable at busy times as it has a controlled crossing of the A71 but I preferred accessing the campus on the north side as you are then traffic free all the way through the campus. I guess it's possible to get to Harmiston Walk from the toucan but I didn't hunt it out.