Chicken mites and lice do not infest humans. They may crawl onto your body while you are handling the birds, but they will not bite and will leave soon. If you are really worried about it, take a shower after handling your birds and all the lice will wash away. You should be careful around your parrots, as chicken lice can probably infest other types of birds.
After you dust the birds, dust them again 7-10 days later. This will kill any new lice that hatched from eggs, which are not effected by the Sevin. If the infestation is severe, you can dust 7-10 days after that dusting, as well. Also, dust the coop with Sevin or spray it with another mite/lice spray to kill any lice living in there. The Sevin dust bottle won't say anything about being used on chickens, as it is not sold for performing that job. However, it still works fine, and lots of people use it.