Once you've decided to put those pinned projects to actual use, the first step to getting your party together is creating your guest list. Before making your list, you need to figure out the maximum number of people you can host. How big of a space do you have? You'll probably need to work at a table, so you can really only host the number of people that you can seat comfortably.
Once you have your list together, consider how you want to get the word out. This casual type of party makes an Evite an easy way to go and there are lots of cute designs to choose from to get your guests in the spirit of your Pinterest crafting party. Or, if you're more of a mailed invitation kind of girl, you can always get a cute, pre-fab version at your local stationery store or even create and print your own if you have some basic design skills.
But if you really want to set the stage for the evening and get the ladies in a crafting mood, why not pick a Pinterest invitation craft and use that as your invite? There's lots of great invitation inspiration on Pinterest that won't take much time or break your budget. You can stick them in the mail, or if your guests live close by, hand-deliver them to save on postage. Another fun idea could be to create a pinboard of highlights of the evening and send it to your guests.