In reply to monkey1:
If you want something a bit different then the Croix de Toulouse above Briancon gives a great birds' eye view of town and the forts.
The VF on the l'Yret at the top end of the Guisane valley is good fun, and gives you a summit.
That on the Aiguillette du Lauzet also gives you a summit, and is more of a 'complete' day (bit of a walk in, etc.)
Personally, I wouldn't bother with the one at Pelvoux - it's short, easy and unexciting... could be done in the evening whilst (I presume) camping at Ailefroide?
There's also one up towards the Col de Pousterle (other side of the valley from the les Vigneaux one) - like the Pelvoux one, if you're only doing one, it's not worth making it this one!
Have a good trip.