You may find that either one or the other promoter has a tight contract that doesn't allow any competition. Eg; your infomercial provider may consider bookshop or internet sales could restrict their own sales. So they'll consider that it's in their best interest to tie you up pretty tightly in constricting clauses.
You'd need to know about that cross-over element from both producers before you went ahead.
You'll also need to know either of your promoter's forward intentions. Will they publicise for a given period, or sell only to meet an internal sales target or go with you as a long-term investment?
Looks like you've got some serious questions to ask them. Keep us in touch!