Another factor not yet discussed is the accuracy of GPS. Typically, with a good satellite lock the accuracy can be as good as 10' on
consumer grade products.
But in poor conditions you can be hundreds of feet off. So with two GPS units, the accuracy can be off by 20 feet or more.
if the intent of your project is general direction, this might not be a problem. But you listed having a laser. If your trying to keep a laser pointed from one unit to the other, and keep it on target, your going to have difficulty.
You will need high quality commercial or military grade GPS gear to get closer to keeping a laser on point of a moving object.