Answer: Keep in mind that the first flowers will be male to assure a good ratio for pollination, so if they all look the same so far then odds are pretty good that they are all male. Female flowers should follow soon. Here is a really good comparison photograph of gourd flowers; they are in the same family so the principle is the same: http://users.owt.com/jdixon/growing.htm
Good luck with your pumpkins!
Q&A Library Searching Tips