Hi Sharynn! Thanks for visiting planDisney.
It sounds like you've read through the
Costume Guidelines and
Park Rules and are concerned your hammer could be interpreted as resembling a real weapon. It's great that you've taken the time to familiarize yourself with the rules and want to stay in line with them. No one wants to have something confiscated.
While I can't give you a hard and fast answer, I've seen Guests dressed as Thor carrying Mjolnir replicas at the
Oogie Boogie Bash - A Disney Halloween Party, which is very similar to what you're describing. Rules change, however, and I think the hammer could potentially fall into a grey area. While I don't believe your accessory could be mistaken as the real deal being gold and squishy, it is ultimately up to security's discretion whether an item can safely enter the park. There's always the possibility the hammer wouldn't be allowed inside. I suggest you have an alternate plan in place, such as running it back to the car or your hotel room. Otherwise, you'll want to leave it at home if the chance of it not being allowed in is a total dealbreaker for you.
Take advantage of photo downloads from the party being complimentary. Take all the pictures you want with the talented Disney PhotoPass Service photographers. We used a picture from a party as our holiday card photo last year. I went to a lot of work designing our costumes, and it sounds like you've really put in the effort too. Capture the fun for posterity!
I hope this helps.
Elizabeth