Welcome! I am an avid tandem rider with my DH - started out on an MTB tandem, but now we only ride on the road. We also race.

Tandems are a GREAT way for a team to ride together. HOWEVER, as already noted, you haven't said how much you have ridden together already. You may or may not know that tandems can also be a BAD thing for a couple.

As a stoker, here are some things that you need to remember:

1. Your wife is giving up all control - think about how you would feel in her shoes.
2. COMMUNICATE, COMMUNICATE, COMMUNICATE! Tell her when there are bumps in the road. Tell her when you are making a sharp turn. Tell her when you are going to stop pedaling, shift, stand, etc. Tell her, and tell her again. Likewise, she needs to communicate to you, and you need to pay attention. She may ask you to coast, or to stand at some point.
3. Make sure you have lots of spare chain and tubes. Four days is a lot of riding, and you don't want to be stranded with a broken timing chain or a flat (or worse - we once had to "scooter" our tandem home from 13 miles out because of a blown hub...).
4. Never ask, "Are you pedaling?" or "What are you doing?" Both things that will get you the silent treatment.
5. Remember that a gear that is comfortable for you to push/your comfortable cadence may not be for her - check in from time to time to see how she is doing.
5. HAVE FUN! Make the experience enjoyable for both of you. I hope that you will both love it as much as we do.

SheFly