I use fan palm fronds as
kindling to get a burn going and also as "flame recovery" when too much
wood gets put on top and things get smoky. Palm fronds make excellent biochar, just keep them from burning too fast as Douglas mentions. Using a pit is a good idea, so all you need to do is keep active flame across the top to prevent the embers below from turning to
ash.
Date palms are pretty spiky down toward the base, so you're going to want good gloves and safety gear. Depending on the size of your pit, you may find that cutting them in half makes them easier to handle and lay in the fire.
Getting biochar into sandy soil is a game changer for
water retention. If you can show the
local growers how to do this, you might make a lot of converts!