Assuming you are traveling from A (Sault?) to Grenoble, I actually think that you will find the small climbs enroute to Embrun harder than the rest of the route. I haven't done that particular stretch, but it looks like there should be quite a few short climbs and those are often harder (in my mind) than one big climb.
After Embrun you are simply following the Durance river to Briancon. Embrun is at ~800 metres and Briancon at ~1200 metres. That 90k should mostly be a gentle, almost not noticeable, incline.
As has been mentioned,
Col du Lautaret out of Briancon is a very easy climb by Alpine standards. The last few kms are a little bit harder, though, but with low enough gearing (that you'll need anyway on a tour in those regions) it's just a matter of taking your time.
(Personally, I wouldn't miss doing Col d'Izoard when being so close to it (it's basically a detour between Guillestre and Briancon).)
I'm sure you'll find five days plenty
.