You will need some herbicides with what ever you plant.

Dual will work with pumpkins and you could also plant some sweet corn in with the pumpkins.

Maybe add some pole beans like the natives did.

What would happen if you applied Dual and drilled soybeans.

Then plant pumpkins and sweet corn in the soybeans.

Maybe go with a full residual program and remove 3" of soil where the corn and pumpkins get planted.

Another option is plant everything, then put buckets over the corn and pumpkins, then apply bean herbicides.

If the field is wet maybe bring in some soil where the corn and pumpkins are.