This is peripheral information but might help rule out some searches ...
And the use of the female name Glenorchy, and Margaret's parents' names at her death, confirm that you have the right Archibald in 1851, Annette.
From the IGI,
Margaret DEWAR m Alexander STRACHAN 1849 Liff Benvie & Invergowrie, Angus
From the IGI they had (all Dundee):
Glenorchy 1849, Joan 1852, Alexander 1854, Jessie 1856, Glenorchy 1858
Presumably Glenorchy b 1849, and Alexander who was 1 in the 1851 census did not survive.
In 1861, as STRAHAN, in Dundee are Alex 34, his children Johanna 8, Alex 6, Glenorchy 3, and his sister Janet 28.
A free search on ScotlandsPeople, refining the parameters, finds a death of Margaret STRACHAN, other name DEWAR, mother's maiden name OWER, age 27, in 1858 in Dundee.
And this is probably
Glenorchy DEWAR (another sister of Peter) in 1891 - Glenorchy KEIL 68, keeps lodgers, Dundee, b Perth Perthshire. The name Glenorchy KEILL (yes, an extra 'l') also occurs in Liff & Benvie in 1891 - young Glenorchy is aged 4 and her father John perhaps/probably a son of the older Glenorchy.
(I found Glenorchy snr as KEILL in the 1861 in Dundee with sons Archibald 9 and John 5. The transcribers presumably gave up on her given name; it appears as 'MA' - I wonder what the original has! And I wonder how they've mangled her name on other censuses?)
Glenorchy snr - surname KEILL, other surname DEWAR, died in Dundee in 1894 age 73.
JAP
PS: Here is a link to the earlier thread on Peter JEWERS:
http://www.rootschat.com/forum/index.php/topic,258141.0.html