The first puzzle was figuring out what to do. As the letter was read aloud, ending with "...this letter is your first clue...", the obvious thing to do was inspect the satchel and find the letter. On the back of the letter (shown below) were a variety of words in various orientations. Many of the words referenced various locations nearby.
Solution
In the home town where most of the family grew up and went to school, there has been a tradition covering at least 2-3 generations of folding love notes called Kindess of Bearer (commonly known as KOBs). The words "kind" and "bearer", and the 'o' in "to" were all bolded (as seen above). The challenge was to fold the original letter as a KOB, and see what it said.
There are various ways to fold a KOB; we included one way specifically folded in the satchel, along with step-by-step folding instructions by example:
More specific information on this folding style can be found on this WikiHow page.
Unfolding the KOB included in the satchel, and then re-folding the original letter in the exact same way revealed the words "TURN THIS OVER" on one side of the KOB and a location name on the other side. (Each team was sent to a different location; in the example shown above, the KOB had the words "TOP OF STAIRS TO TOWER".)
Continue on to Challenge #2: The Map Grid, or see the results of this challenge.