Yeah! Higher grade pumpkin products give you more food pellets; every product has a base amount of pellets they can make, and then the grade counts as additional pellets. If you go to the Pixpet Food page and hover your mouse over the "Turn Into Food" header, it will display the conversion rates, but here's the table again:

Pumpkin Flowers: 30 + grade
Sprouting Pumpkins: 60 + grade
Grown Pumpkins: 120 + grade

So if you had a grade 50 sprouting pumpkin, it can be converted into 110 food pellets

If you want more seeds, I've found the best way to get them is by helping other users' pixpets hatch.