Hello Carl. Unfortunately, your ancestor has the most common name that there is for Gelling. I think every Gelling family had at least one John, which makes it very difficult for us folks trying to figure them all out. I looked at the IGI, and there were 6 listed within 2 years either side of 1799:
22 Jan 1797 Braddan s/o John G & Margt Kewley
29 Jan 1797 Braddan s/o Philip G & Anne Kewn
20 May 1798 St. George Douglas s/o Ann Gelling
11 Dec 1798 Malew s/o John G & Ann Brew
24 Feb 1799 Braddan s/o Thos G & Elizth Kelly
16 Jun 1799 Douglas s/o Robert G & Ann Clark
(next one was 1802)

The last 3, if still alive, would be 80 years old at the date you gave, so would be the first candidates to check out. The IGI is not perfect or complete by any means, so there could be others.

I don't know any of them on the list, though the 2nd one may link into my family as I have the name Philip. I haven't gotten far enough in my own research yet to know.

As a Gelling, I wish I could be more help for you. My family also came to Canada about 100 years ago and I live on the other end of the country, Victoria. We visited Nova Scotia this summer for the first time and fell in love with it.