Ok, the reg that i've always quoted in reference to this question is from the interpretation section at the front of the CARs:
7 (d) [p30 of the online regs]
an aircraft that is flying or operating for the purpose of, or in the
course of:
(i) the personal transportation of the owner of the aircraft;
(ii) aerial spotting where no remuneration is received by the
pilot or the owner of the aircraft or by any person or
organisation on whose behalf the spotting is conducted;
(iii) agricultural operations on land owned and occupied by the
owner of the aircraft;
(iv) aerial photography where no remuneration is received by
the pilot or the owner of the aircraft or by any person or
organisation on whose behalf the photography is
conducted;
(v) the carriage of persons or the carriage of goods without a
charge for the carriage being made other than the carriage,
for the purposes of trade, of goods being the property of the
pilot, the owner or the hirer of the aircraft;
(va) the carriage of persons in accordance with subregulation
(7A);
(vi) the carriage of goods otherwise than for the purposes of
trade;
(vii) conversion training for the purpose of endorsement of an
additional type or category of aircraft in a pilot licence; or
(viii) any other activity of a kind substantially similar to any of
those specified in subparagraphs (i) to (vi) (inclusive);
shall be taken to be employed in private operations.
So, any number of pax can be carried under a private category as long as they're not being sold into slavery.