It's sunrise you want to see (the temples face east) - the temples are in the shade at sunset (or after noon). Could you take a cruise back to ASW? There are about 6 cruise lines, maybe more. You usually board the ship day 0, sail after dawn on day 1, visit some sites long the way (accessible most easily by boat), moor somewhere on the lake day 2, get to Aswan evening of day 3, and disembark in the morning after a tour of the temples by the high dam.

The trouble with the caravans is that you may not arrive in time for sunrise (you see tour busses arrive one every 10 seconds for several minutes, all discharging lots of tourists who need to go through security).

Do be aware the admission tickets (valid only one time) and EGP 80 each.