At this show, you can see some photographers who have access to the planes, beyond the barriers. I think you should contact the managers of the airfield & show for that.
You can also find a good place behind the barriers, if you come at the show early in the morning : some places allow to see the planes taxiing very close.
There is also a VIP pass that includes an access to an elevated tribune with seats... (expensive, about 150 €)
La Ferté is just about 45mn by train from Paris (centre). quite easy to find lodging. there are also numerous hotels at various prices in all the towns around. Camping places also...
There is also a place near the airfield for the camping cars.
I think the best is to come by train then walk about 20-30mn to the airfield. Coming by car if not very early is a nightmare, as the airfield and the parkings are on a hill top with only one little road for access. From 9-9:30 AM, prepare yourself to spend 2 hours in your car...Earlier of course, it's done in some minutes.
Here you can have some more information on La Ferté Alais and the Salis association (AJBS)
http://www.ajbs.fr/index.php