Pumpkins will not cross with melons,cucumbers,muskemelon.
C Pepo(Field Pumpkin)will cross with Zuchinni, or ornamental gourds, but they will not cross with an Atlantic Giant.
Now most Winter Squash(C Maxima), such as Cinderella, Blue Hubbard, Queensland Blue, will cross. It will not affect the cross this year only the seeds.