I'd get a helper or 2, and quickly gather up ALL of the scattering keets while someone keeps the Hen back (she will be EXTREMELY viscous and aggressive, so be ready for her to attack you and not cooperate... and the keets will scatter like ants so be ready for that too).Yeah, we have nine keets. 6 grey pearl/pied and 3 lavender? (Not so good on my colours
yet!). Now to get her to take them into the pen. Any ideas?
Put the keets in a bucket or box inside the pen that is set up with high protein starter food and a shallow water dish or chick waterer with marbles or clean rocks in it to keep the keets from drowning in it... leave the pen but make sure you can reach the bucket or a box to tip it over and let the keets out. Momma Hen will come to the keets' peeping cries. Shut her in as soon as she's in and let her have her babies back.
You might want to steer clear and leave her and her brood alone as much as possible for a few days to let her settle down/adjust. Guinea Hens are usually very mean/nasty when it comes to protecting their keets, so don't turn your back on her when you are feeding and watering them, she will get you if you give her the chance.
If you have other birds in the same pen, they may kill the keets... so you may want to get the Hen and keets all corralled into a separate area of the pen and then prevent the rest of the flock from getting at/to them for a couple weeks. If you don't keep them contained, as soon as you let the Hen and keets out she will most likely wander off with them (and possibly lose most of them) and then just bed down where ever she feels is safe (which usually isn't a safe spot). She won't want to bring them back to the pen each night, you will either have to keep her penned until the keets have grown some and not so fragile, or do the gathering routine each evening. It's up to you as to when to let them out but the longer you keep them penned the better chance they have of making it once you do let them out.
Good luck, and we'd love to see some pics!