Are you saying that these particular hens have shown a pattern of broodiness, or are you going by the reputation of the breed?
Even within the breed, there can be a wide variation in behavior. I have had several hatchery Buff Orpingtons, and only one ever went broody on me. I have had quite a few Silkies and Bantam Cochins, too; based on reputation, you might think I'd never have eggs, lol.
With most of mine, just keeping the eggs collected kept them off the nest. There are lots of threads about breaking up broody hens if one does go broody and you don't want her to, most involve keeping her bottom side cool (a lot of people use a cage with a wire floor as their "broody buster"). No method is totally foolproof. I once had a particularly stubborn Silkie that spent months "brooding" nothing in a wire-floored rabbit cage; I finally had to let her hatch a couple of eggs just to get her up!
But barring unforeseen, really extreme behavior like that Silkie, you shouldn't be put off from the two birds you mentioned simply because of their broodiness.