Do you have place in your house that don't receive direct sun or do you want to grow plants in your living room, dining room or bath room? Luckily there are plants that grow without sunlight and you can grow them indoors.
Ballpark the temperature. Place the dutch oven in the coals and then hold your hand over it at the level of the sides. Count backwards by 50 starting at 550 (550, 500, 450) until you have to remove your hand. That will give you an approximate temperature produced by your coals.