As far as others on this site, you have already heard from Paul Robinson who posts a great deal of information about the Hyndman family on this Hyndman Family Genealogy Form. Click on his name and check on his Hyndman family posts which list Antrim Hyndman's and the connections to Antigua, Australia and Canada.
His post 309 has this about the Australia connection:
" Georgiana Lucia Gordon McCrae (1841-1908) m. 10 June 1862 Robert Hyndman, son of Robert Augustus Hyndman, solicitor of Dublin, and Jane Moody. He d. 4 Nov. 1913, with issue, 4. Robert Gordon Hyndman (1863-1901) m. Edith Helen Black in New Zealand. 4. Lucia Jane Hyndman (1865-1948) m. Julian Campbell Ridgway and had...."
Post 257 in his reply to my 2003 inquiry about his interest in the Hyndman family was this:
"Actually, my main interest in this family concerns their marriage into the Macaulay family . Are you familiar with this Northern Ireland connection? In truth, I have access to quite a bit of information concerning the Hyndman family of Northern Ireland that was recently sent to me. However, I cannot release the information without first gaining permission from the sender. I am hoping that in due course he will put it on line or allow me to do so as it can answer many questions that you and a few other researchers have."
His Posts 254 and 255 feature the Prince Edward Island, Canadian line of the Hyndman tree, those directly related to my family.
A Canadian cousin of mine,S. Hope Hyndman has done a good deal of research on the Antigua Hyndman's as well, you can find her at Post 207 on this forum and one other potential contact is James Lenaghan (Post 206 from 2001)who said:
" If you are interested in the Hyndman family of Antigua, PEI and Northern Ireland - you're in luck. Recently a cache of Lenaghan family papers has been discovered in Canada. My family was connected by marriage and business to the Hyndman family in Antigua, PEI and Ireland. Among the surviving materials is a short write up on the family of Thomas and Eliz Hyndman, along with numerous letters which mention the Hyndmans in Antigua. According to this information, their sons, Robert and James went to PEI."