As you may already know (and I am sorry if you do), dry hoping is going to give you more hop aroma in your final product. I love hops so dry hopping has changed my life! Typical dry hopping doses call for 1-2 oz of hops depending on what you are going for. So, 3/4 oz seems almost perfect to me for a pumpkin ale. I personally would not want my hops to overpower the pumpkin taste given it is a special beer for a special time of year.
Willamette works well for American-style ales and even lagers. It seems pretty popular so I would imagine you will not end up with something totally horrible at all.
Do not just take my word for it; weigh the options above and the facts you already know and make a decision that works for your preferences. That way the outcome is a NEW beer that is your very own... that you made! That is something (good or not-so-good) you can and should be proud of.
Let me know how it turns out- and good luck!
-Ritalin