I said I'd post Tauck's response to the question when I received it. Here is what Tauck sent me:
A travel wallet would be used for guests with a tour that has been canceled by Tauck. We would place your money from the current tour that has been canceled into the Travel Wallet so that when you are ready to rebook book, you can use the money in the travel wallet towards the deposit.
A dreamsaver is a credit for the cost of your penalties if you cancel a tour that has not been canceled by Tauck. The dreamsaver credit can be used towards the final payment of a future tour.
Hope this clears up the differences.