Long Range WiFi Setup - Noob Question

Hi everyone, sorry in advance for my noob questions but this is my first time ever trying to setup a wifi network over long distances.

I live in a rural area and cannot get any broadband internet at my place. My father and brother in law, however, can get it at their houses about 0.8 miles away from me. Here's the distances and obstacles between all three points:

My father in law's house would be the broadcast point(A) with a WRT54G.
My brother in law(b) and my house(C) would share the connection.

From point A to C is approx. 4370ft.
Inbetween point A and C there is approx. 1000ft of trees/houses.
Point C is approx. 46ft higher then A.
With 1000ft of interference between the two points could any connection worthwhile using be established?

From point A to B is approx. 540ft.
Inbetween point A and B there is approx. 500ft of trees/houses.
Both A and B are at the same elevation.
Any issues with signal strength between these two points?

Please let me know what type of antenna's you would suggest for this type of setup. If the setup between point A and C can't work, could it still work between A and B?

I was originally thinking point A and B could have 9dBi omnidirectional antenna's. That way they can still connect their laptops ect wherever they might be in their yards or houses.
At point C I was thinking a 24dBi parabolic antenna.
Would these antenna's work at all? I've heard that yagi antenna's work better through trees. Is this true?

Thanks in advance!!

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