Sorry to hear about your dogs.... can be a real bugger at times huh...
It all depends on what bred of Geese you have for the half acre (wether it be toulouse, chines or Xbreds). It also depends on what this half acre is like (wether it be rocky, dry, sparce, not much grass, not much water, and if you are willing to supplement their feeding with grain of some description.
You can have geese on half an acre...but it depends on the above I have found out. Of course I give them grain, so they are fine, and I definetly do not have too many on the on small patch of land!
Hopefully others will help you in what breeds of geese would be best or wether it just be Xbred farmyard geese.
Do not get me wrong though, the more land the better for geese.
They do not need a dam either.
(the bigger the breed the more water though usually).
Geese are hardy, and can usually tolerate lots.
Some breeds are much better at guarding and protecting them, their family, owner, and home than other breeds of geese.
Some breeds like to fly, others don't.
Geese might deter snakes, and you can pick up when there is trouble around, but geese will die from sankes and if it is an adult gander, or gosling, geese tend to get upset and mope around for days and it does hurt them.

(not as bad as swans though).
From memory Tribe of Honk's website actually gives you the pros and cons of geese/each breed I think...and I think that's what you need to consider to help you along.
You cannot go wrong with geese I say.... go for it!
(just do a bit of research first!)
Keep the grass down yourself though bigtime Sara.
P.S. Peafowl (peacocks), warn of snakes, and any other thing like eagle etc, and will keep snakes away. They also don't need the amount of room and are as wild as what most people think they are...all depends on how you bring them up.
I have heard Guiena Fowl are good too....
Cheers,
