Except for a couple studios nudes (male and female) I did 20 years ago (which I think as more as figure studies rather than portraits) and some nudes in the environment around the same time (again not portraits), my portraits have been limited to my three boys.
At first I used an SX-70 camera and did maniplulated polaroids. I stopped doing those when they learned to crawl and they would no longer stay where I put them. I now have a series-in-progress of the Boys in the environment, which I feel are more along the lines of portraits -- though if someone was to argue with me about which genre they actually are, I would not put uip much of an argument.
The Boys and I were taking 1 to 2 mile hikes in the redwoods by the time they were 3 yrs old. I started taking the 8x10 -- and when I found something I wanted to photograph, I'd get the lunch stuff out. While they were eating, I'd get the camera out and make an exposure (otherwise keeping track of 3 four-year-olds while one's head is under the darkcloth is difficult -- I have a few stories I have never told my wife!)
Once they were 4 or so, I could start having them pose for me with exposure times of 30 to 60 seconds. And once they hit 7 or so years, I could spend more time under the darkcloth without worrying about the Boys exploring on their own around me. For my landscape work I tend to wander around the landscape looking at the light until I am moved to set up the camera -- I rarely go out with a specific image in mind.
With the series with the Boys, about 50% of the images are in the locations that are chosen from previous experiences with a specific place. Generally I take a few landscape images and let the Boys explore, climb trees, play in the creeks or whatever for a couple hours -- perhaps after hiking a hour or so. This burns up some of their excess energy and also grounds them to the environment we are in (mini-lessons in geology, botany, wildlife biology, etc get tossed in, too).
Once I have the camera is set up and generally composed and metered, I call to the Boys and have them pick their spots and poses within the frame -- with minimal coaching. With such long exposures, I do not expect stock-still faces...I just like to be able to see the facial features. I generally take two shots of a scene, and can occasionally talk them into to posing for a second set up in a different location -- but I am happy to get one.
I also have a second series of environmental porraits of the Boys using a Rollieflex and color negative film -- these tend to be closer up than the 8x10 and understandably a bit more spontaneous. I have not printed any color recently (RA4) and have a backlog of possible negs.
PS...this ended up being quite a book...thanks for reading!