80 acres is not that large, so most two way radios should work.
You may want to look at these (they do not have GPS) as a basic inexpensive set:
http://www.buytwowayradios.com/produ...-1000-vp4.aspx
For radios with GPS, we have these:
http://www.buytwowayradios.com/produ...-rino-120.aspx
You could also use a base station radio at the house for a bit more clarity and range.
While you "could" use them in Europe, you would probably also get in a bit of trouble since they are not approved for use there and may interfere with emergency radios, etc... So you would need to get European approved radios.
Just give us a call and we will help you out. 1-800-584-1445