You can cut off the tips to induce more female
flowers to get more smaller pumpkins, or just pull off all the newly set fruit to pump more goodies into the existing fruit to get less, bigger pumpkins. Generally though, for a family situation, more smaller ones is better than a few big ones as they are harder to use up fresh if they are huge. Fun to watch grow though if they get massive. (My best is 15 Kilograms, Queensland Blue variety. Yummo. I think that's about 45 lb or something in old speak.)