When we penned or gated the floor was pee and poopable vinyl and easily cleaned. A pen would be best I guess as some dogs will chew the walls. We penned in our kitchen and had no damage. Imagine that, a Lab who doesn't chew. We were lucky.
I really, really am against crating to force a young puppy to hold on but yours are of an age where they should have the control needed by now. I realize you are attempting to potty train and can't since you have to work. Darn work, cramps all our style.
So if you did have to crate till they learned control I'd recommend the DDC and a friend to come in and walk them. More than once a day.
Given their ages I think that would be good even if you used a pen or gates but you could cut down the outings once they've learned the potty. Though Bullmastiffs are not as active puppies as Labs are, I thinK? I have a Lab. The BM across the street, RIP Mocha, sure could not keep up to my Lab.
OH crap, better not call them BM when we are talking potty. BMtiff?
AND, we'd like to see some photos. Please? The BMtiff on my street was also a rescue and the most gentle, loving, wonderful dog you could imagine. OUr whole street mourned when she went too young, age 7, of cancer.