Heh heh - actually, if they are fed pre-killed prey, you might get them to come investigate by wafting the smell of a thawed mouse or rat in the general direction you want them to move toward. I wouldn't let them see it, because they might strike and snakes don't have great visual judgement - they could very well get her in the face! These guys don't have fangs, but their bites will still draw blood and they're no fun.
The ball python will be more likely to coil up, and you could get some cool shots of her holding him in "ball form" in her hands. It sounds like he's the peftect size to fit in her hands when he's all curled around himself. Ball pythons tend to stick to the ground more than climb, so he may not be a shoulder snake - or he could be, if she's gotten him used to riding around on her.
The red-tailed boa should be no problem with the kind of shots you want to do. I used to have one - they're wonderful snakes. They have really gorgeous patterns, too. They look like living granite sculptures, flecked with grey, silver, black, and pink. It's small for a red-tail (they can get up to about 18 feet!) but she might be the right snake for your S-curve shot you're thinking of. They are good climbers and have a tendency to try to get up high to feel secure, especially as juveniles. So she can probably be coaxed into climbing slowly up toward her owner's face by doing "the hand ladder," where the owner will keep moving one hand in front of the snake for her to climb onto. If she raises her hands by an inch or two each time she alternates them, the snake should start stretching upward.
Good luck! I hope you'll show us the results when you're done! I love snakes.