Here is the draft for distribution.  In addition to the customer-friendly 
"looking forward to meeting with our business partners" language I know 
you'll include, I'd suggest including something like the following:

Attached are drafts of the proposed tariff provisions (including the form of 
Transport Option Amendment) and a filing letter.  We are providing these 
draft documents to you in advance of filing them with FERC as part of a 
good-faith effort to resolve any remaining issues with our shippers prior to 
filing.  The drafts are for purposes of discussion by workshop attendees 
only, and we ask that you not distribute them to persons outside your 
company.  Additionally, while we hope that these drafts are close to being in 
final form, they are of course subject to revision and final management 
approval prior to filing with the Commission.