The path loss thru the trees will be much worse in the summer than when they are dormant. Lower freqs would have less loss so, a 2.4 ghz link is not the best choice but we have no choice here.
In that case we need to get above them if possible. Ant height gain is offset by feedline loss so use good (large) coax. LMR 400 is what most use for long runs of 802.11 but it has a loss of around 7db/100ft. Plus, if it is like the earlier version of the low loss RG213 coax cables, I've used in the past, there will be condensate build up in the dialectric over time. In three yrs it was useless. Check out RF Parts co for Andrews Heliax.

I have a few large rolls of used 7/8" if needed.

At least your noise floor will be low way out there in the sticks.

For the hill look for a polar of the highest gain yagi or a panel ant with the -3db beamwidth that will work for the two locations. If a E and H plane pattern is not provided stay away as a gain spec is meaningless if you don't know where the signal's going.

Look around at the Radiolabs site. Plenty of info there.