Is your tom strutting for the ladies and do they seem receptive? You'll likely see him breed them unless you're from home most of the time. Once they're successfully bred, the eggs will be fertile for a couple weeks. He will keep them fertile (once he figures out how it's done.)
I've heard of BBW hens successfully hatching eggs but if you want to be sure you have poults for your son's project, it would be better to collect some to incubate yourself before you allow the hens to sit (if they're inclined to do that.) BBs are especially bred with fast growth and big heavy breasts in mind. From what I've read, they can have difficulty sitting on a clutch without breaking the eggs.
You'll want to make sure they each have their own nest. Too many mamas tend to clumsily tread on babies. I haven't had real good luck with heritage turkeys raising poults, either. They sit faithfully and hatch their broods but they've not been especially good at taking care of them. I have one who ended up sharing a nest with a chicken. Five poults & no chicks hatched (chicken eggs were not fertile). Between the two of them they've managed to keep two poults alive and that's mostly thanks to the chicken, I think.
So... if you're invested in live poults with the turkey hen providing care, you'll want to give her a lot of support and be careful not to fall in love with the babies.
BBW mamas are a very cool project. They're such sweeties. Alas they don't live very long. If you'd like to keep them alive as long as you can, you'll need to restrict their feed. Sitting on eggs, they naturally won't eat much—which for their health, is likely a good thing. Best of luck with your endeavor!