My grandson is a professional arborist and climbs trees like a well trained monkey. He has mounted antennas on tree for several others.
OK, so that's the hard part out of the way.
What you might be gathering from all this is that there's a cost vs. benefit thing you need to look at:
Costs:
Long run of cable will be expensive.
Risk of damage to cable.
Feed line losses are accentuated by the long cable length.
Lightning risk.
Difficult to maintain/repair the antenna system without calling in your grandson.
Benefit:
Higher might work better.
"Street Cred" factor, AKA bragging rights.
Since these frequencies will skip off the atmosphere, raising the antenna won't necessarily make it work better for talking long distances. On the other hand, it should give you really good local area coverage. Putting a good antenna up as high as you can will increase the direct line of sight "radio horizon". In other words, the amount of area your antenna can see is much greater being at that height.
Where you need to be careful is if you are going to put this much work into it, don't cut corners. Invest in good coax. Hobbyists love LMR-400 and many are under the impression its some sort of Holy Grail of coax. It isn't. It's halfway decent stuff, but pretty low on the list for commercial use.
Not sure what your budget is, but if you are going to put the work into this, you might want to invest in better coax now. Better coax will get more signal to AND from the antenna (it works both ways).
You can run some calculations here by inputing your cable length, power input and selecting various types of cable to see what it'll give you.
At 27MHz, Times Microwave will give you 1.581dB of loss over a 250 foot run. That translates into 4 watts coming out of your radio and 2.78 watts making it to the antenna.
LMR-600, which is a bit bigger, about 1/2" diameter, will have 1.0dB of loss, and give you 3.17 watts to the antenna.
LDF4-50A Heliax cable will have 0.848dB of loss, and about 3.29 watts out at the antenna end.
While going from 2.78 watts at the antenna to 3.29 watts at the antenna isn't going to make a huge impact, it does also help on the receiving side. In other words, you'll get a bit better reception.
What ever you install, you really want to make sure you support the cable correctly. The weight of 200 feet of cable pulling down will damage the connector and cable over time. I'd leave a loop at the top, and anchor it on it's way down, leaving some slack to allow for tree growth and movement.
If you really wanted to be different, feed the antenna with ladder line. It'll have even less loss.
Heck, while you are at it, have your grandson put a pulley and a length of line going up into the tree. Using a high tree like that to hoist up long wire antennas, dipoles, etc. would be pretty dang useful for other things, too.
