I am defining major and minor channel numbers from my Drake product. Afterwards, do I provide the new major/minor channel information to the people doing the channel mapping?

No, the required information for mapping purposes is still the actual RF channel, QAM mode, and MPEG number. When the change is made to the major/minor channel numbers, this is defined in the VCT (Virtual Channel Table), and this information is NOT relative to set top box mapping because this table is ignored.