Obviously, you have enough voltage at the base (24V) and the length to the LEDs (100') max is well within the tolerance of your supply voltage.
Consider using an adequate guage wire (16AWG) and place a small regulator circuit at each interval (length).
Using a regulator at each node 50', 75' & 100' will regulate the voltage to the desired amount required by the LEDs.
The regulator does not need to be too technical, a simple Zener (1W) along with a proper sized load resistor will work.
Furthermore, perform a test on the ground to make sure your interval regulators will operate properly.
Example:
Stretch the max length of wire on the ground and at each interval place a regulator, the latter will allow an easy painless way of testing your setup.
Twist the wire for more integrity along with a clean installation and use a decent wire (teflon coated/silver).
Remember, the NEC does not even begin to calculate a voltage drop until 100' in reached.
However, in your case the max would actually be 200' since you must also factor in the return length.
Furthermore, a calculation is not really necessary since you are 100% above the required voltage at maximum length.
Footnote:
I remember awhile back designing advanced accelerators for the Trans-Atlantic cable.
Most common people believe solid state amplifiers are placed on the ocean floor to amplify the communication signals since the length is extremely long.
In truth the latest engineering design consisted of specifically placed 3 meter lengths of doped Rare Earth erbium (fiber optic) that would continually accelerate the transmission.
Rare Earth Erbium is located deep within the Earth and when doped with the proper elements is highly light sensitive!