I don’t know much about ducks, but I think the hatching process is pretty much the same as chickens.
Chickens usually only get off the nest 10-20 minutes a day for food water and dust bathing.
Maybe try building the pekin a little nest box, easy. Search on YouTube just using a big container or wooden box!
Thus, she’ll be able to sleep there and keep her babies warm at all times.
Sorry if I’m wrong, but either way a nest box will be easier!
Hope this helps.