A.A.
Have a housewarming party when the house is done! Invite everyone who helped in any way. Have some food and beverages and just enjoy their company. It doesn't have to be a six course lavish sit down dinner, just a good old-fashioned get together so people can see what they helped build. If you want to be creative, maybe even put some little signs or post-its on things people specifically helped create....such as a sign on a banister that reads "Aunt Susy helped nail me to the wall!" or a note on a couch that says, "Uncle John almost threw his back out carrying me in." Make sure to take a moment and say a little speech to everyone like a toast to thank them for all the work they put in. Consider taking a picture of everyone together or with separate groups of people and than framing it in the entryway to your home with a cute saying to remember the help they gave you. Of course, plain old hand written thank you notes never go out of style and don't cost much either. You are very fortunate to have such great friends and family, best of luck!