How old are your geese? And by "flighty" are they just stretching their wings or are they flying over the fence?
I think the birds are gorgeous with their wings full and outstretched. Also the ability to fly is part of their natural defence.
As with chickens, if you clip these flight feathers too closely, you can actually cause a blood feather to bleed profusely. It would be best to have someone experienced or a vet help you the first time.
If it is for their safety, then Dave Holderread's book "The Book of Geese" suggests that as many domestic geese mature, they lose their desire to fly after a year old.