I made one for my in-laws 50th wedding anniversary. Some advice--send along a sample. People will not know where to write or what to write. I suggested if at a loss, simply sign their names.
Iron freezer paper onto your strips and include directions and a SASE. Trust me, you will still be waiting on blocks to finish your project. As always, be flexible. Even though you send out 100, plan on not getting all of them back, so have another back up plan to fill in the holes.
I can tell you that from the time I sent blocks and started receiving them back, 2 of my MIL's best friends succumbed to cancer. To see their wishes/messages 4 months later was a blessing.
Best of luck in your endeavor.