well at the start there is no grass around so getting anything else to grow but vanilla crops is not an option. maybe giving non vanilla rewards in the quest book would help. i mean there is a quest for wheat and seeds? Also pumkins can't be eatten anyway unless you count pumkin pie which would take a long time to make in this pack and could be disabled.
I have modtweaker. I added Harvestcraft seeds to sifting dirt and removed the vanilla seeds. So, instead of getting wheat seeds, you get rice seeds, instead of melons, grapes. That kind of thing.