I think a typical pasture mix would be fine.
One thing I thought, why don't you just "mow" the area you want them in for now, brush hog, whatever, and water it good. New grasses and stuff will come up, and that is what they like. Then in late winter/early spring, "seed" the area so that it is wetted down with rains and the seeds are washed down into the dirt. Then, the new stuff will come up along with the old.
I used to cast pasture mix onto the snow when I lived in Idaho, then more snow would fall on top, covering the seeds, and it would gradually work it's way down to soil level and be somewhat buried. In the spring, it would come up furiously
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Of course it depends on what is growing already in your pasture. Pasture mix is pretty rugged, adventitious stuff, but if you have something already that will take over the world no matter what, seeding over what's already there might not work.
If you do want to keep your geese from one area, I use plastic fencing and T posts pounded in only a little ways. It keeps geese/poultry IN, but does nothing to keep predators out. Plastic fencing is recyclable (ie, you can use it again, use zip ties to make small pieces longer, etc) and easy for us gals to haul around