Recreating board games as Excel files and also in wood working.

Do you mean something like Axis and Allies?
Since copyright covers the artistic value of something, the Excel files are probably not infringing. I'm assuming that your Excel files are basically grids and do not incorporate scans of the board or copied art. Of course, I would need to see them before I could say with any degree of certainty.
Similarly, your cousin's boards may infringe the copyrights if they incorporate the original board's artistry.
It's a tough call, impossible to make on the facts before me.

You are right that a board game might be protected by copyright and/or patent. And even a single copy of a copyrighted or patented work might constitute infringement of the owner's rights.

As a practical matter, it would be appropriate to look at the board games, their instructions and their containers to see if there are any notices mentioning a patent or copyright (often including an encircled-C symbol). The bad news, though, is that a game might be protected by copyright or patent even without such a marking. The good news is that there are a lot of games that are not protected by copyright or patent, either because they were never so protected, or because such protection has expired. The Constitution provides that the patent and copyright laws provide protection for only "limited times."

For an example of a patents for a game, see the link that I have attached below.