I may have some clues as to why you can't find Margaret or William Stowell. Also the reason the children were living with their grandfather, John Looney (Yack).

Look at the burial records of Maughold Parish for William Stowell who died 9 Sep 1833. The record shows that this William Stowell was from Ramsey and was age 57 (b. 1776) when he died. On this same page you will find Margaret Stowell of Ramsey, age not given, who died 11 Aug 1833.

From the Maughold Parish records, this couple had two children Isabel b. 12 Oct 1828 and a son William b. 14 Oct 1830. There is a death/burial record for Wm Stowell "Infant" son of Wm Stowell dated 3 Aug 1836.

It appears that Isabel Stowell is most likely the only one that may still be living for the 1841 census.

I looked for a Margaret Gelling birth in Maughold Parish, but could only locate one for a child named Mary Ann dtr of Edw Gelling and Margt Stowell who was born 3 July 1836. From what I have seen so far in these old records, I think the mother's maiden name was Margaret Stowell, not Looney since it did not indicate such. Also, it appears from the record that Margaret Looney Stowell had already died in 1833 along with her husband. That's why her two children were living with their grandfather in 1835.

I hope this little bit of information helps you in your research.