The mother's instinct is too bring her body/skin (less feathers) as close to the chick(s) as possible to provide them with the appropriate amount of heat and protection. She does this by having the chicks under her, breast and belly, or close to the wing pit, where there is less feathers and more body heat to be trapped.
Having a very soft thick nest made of pine needles should help to minimize the risk of suffocation. The pine needles are strong The needle's length and shape provide good insulation while still allowing ventilation.
Underneath, when there is a thick covering and right amount, they prevent crushing. Its better too have too much bedding than not enough. Lowes usually sells pine needles.
Sometimes a broody turkey will accept chicks that have already been hatched. Provided that they are not too old. This is a gamble, because sometimes they don't accept them. But I have put 7(or less) day old poults underneath broody turkey hens many of times and I have never had an issue. The adopted mother has always been accepting. However, I have heard of others not being so fortunate. You have to really watch them at first. If she is not going to accept them you will know fairly quickly. Its not going to be where she accepts them at first and then changes her mind a few days later. right away she will either love them or not.
But a few days older chick will have a better chance of not getting smothered than a 'just coming out of the egg' chick.
this will also give her practice for next year and hopefully do a better job with her own offspring.
There is a reason why birds, and many other animals have multiple offspring at a time. Mortality rate is high. No one teaches a new mother turkey, it's all by instincts, and unfortunatley, just like humans the kids usually suffer the most from the parent's mistakes.
If all else fails or you opt not to give her any more youngins, then you may need to quarentine her. Limiting her from interfering with other broody birds.