That's cool that you found some relatives. My grandfather did that about 10 years ago, and we had a huge family reunion in Central Wisconsin (Oshkosh) with like, 300 people. It turned out that one of the 300 was a Witness (actually she was just married into the family). Mom was super excited, so then everyone was happy. (We thought we were the only JWs in the family.)
I can't count the times we've ruined something fun by trying to Witness, but hopefully your newfound relatives will just give a polite "no thanks" and move on with finding cool family tidbits.
GG