The link you sent with the pics of the dome style heating was a great visual to understand how to use a heating pad as a heat source. I do believe this would simulate a very natural environment, just based on common sense. Heat lamp was my first option, and everything I read said to adjust the heat temp as they grow feathers, so just raise it a few inches per week. How does the heat pad work in that sense? They just go in it/on it when they need? Would make sense as they would use it just like the would momma! The only worry I have, as I've read, is the fire hazard of a heat lamp. I love the options and appreciate the advise and different opinions. Everyone will have something that works for themI'm all about learning and experimenting, so thank you both for sharing your views and experiences!
As Blooie mentioned, Mama hen does not alter the amount of heat her body puts out. As her brood of chicks grow, she may need to stand up a bit to accommodate them when they all come running for a bit of Mama love. Or she will lift her wings out so they can all burrow under. But, the amount of heat remains constant. With MHP, we do have the option of turning it down, and that is a very helpful feature. I find that when my chicks abandon the MHP earlier than I think they should, simply turning the heat down will bring them back to the pad. And the wire frame is designed so that it can be raised or lowered to accommodate chick size. Chicks get warmed by actual contact with the pad.
When comparing heat lamp to MHP:
With a heat lamp, I have come very close to overheating my chicks, even when checking the temp in the brooder frequently.
This does not happen with a heating pad.
Chicks who are MHP raised, IME are less prone to aggression, and feather picking.
With a heat lamp, the light is on 24/7 (unless it's turned off intermittently for weaning purposes). The chicks never have a period of time when they are all quiet and sleeping. One will start yelling, and be running over her sleeping buddies. Chicks are so exhausted that they do face plant fits of narcolepsy in the food dish, sometimes in the water bowl, or fall asleep standing up until they slowly sink into the shavings, only to have a brood mate go running over their back and wake them back up.
This does not happen with MHP. Tired chicks go into or on top of MHP and take a nap. When they go to bed at dusk, they all go to bed at the same time. They trill themselves to sleep. They sleep all night. They get up at dawn.
Heat lamp raised chicks are terrified of the dark when they first encounter it. They never trill themselves to sleep.
I suggest that you start out with grass in your run. As they devour that, you can add your deep litter materials. Save your shavings or straw from the brooder. Save all of your coop bedding, add yard debris to it.
I know I shouldn't be chuckling, but when I think back to how nervous you were about trying MHP back in the day, and then compare that to your well-written post....kinda like when I first came onto the Front Porch whining because my babies didn't like me and being exhausted because they were so much work, remember? How quickly I went from that to "Well, they ain't bleeding so it can't be that serious!" What a pair we are! 
it's great to have you here!
and welcome to backyard chickens!we're so happy you've decided to join us here
i hope you enjoy your time here.
