Hi Carmel, there is no record of the marriage on Roots Ireland, it would be difficult to know where to look as it is Presbyterian, (40% plus of Church of Ireland or Anglican records were lost in the civil war of 1922/23) so unless we can identify exact demonimantion and hope they have records there is no marriage record, civil records for Protestant marriages commmenced in 1845 and all BMD in 1864.
I looked in the Tithe Applottments from 1824 to 1838 there are a 214 Dickson entries (this is a land tax) the ones in Westmeath are a distance from Athlone and there is one on the Longford / Westmeath border, there is a Robert Dickson who appears to own a huge amount of land in Sligo. This is a distance from Athlone, was the Peek man an officer do you know and would there be a military record, the reason I ask this is it is more likely an officer would marry someone whose family were land owners, Athlone is also on the boundary of Roscommon but I see no Dickson there in the Tithes, however you had to hold land above an acre. See http://titheapplotmentbooks.nationalarchives.ie/search/tab/home.jsp Griffiths Valuation done between 1848 and 1864 is here, there area a number of Dicksons in Westmeath, again as in Tithes some in a place called Killua which is a good bit from Athlone but the truth is without more information we are lost. The icon connection to the year is not coming up now so not sure the year. http://www.askaboutireland.ie/griffith-valuation/
Now Hugh De Lacy is a name to raise an eyebrow, it is rather famous in history and I live in Drogheda where a footbridge opened over the river Boyne circa 2005 is the Hugh De Lacy bridge, I am sure a Google search will bring back plenty on him, basically the Normans arrived here in 1170, mainly from Wales but from all over the place, De Lacy ended up in Meath, and until the late 1400s I think there were two Droghedas on the Boyne, north of the Boyne was controlled by the Verdon family and unbelievably someone of that name was on here about a week ago. De Lacy controlled the Meath side, these people were I think Catholic and after taking over the place were known to be "more Irish than the Irish themselves" assume De Lacy took the catholic side and there was a siege of Drogheda in 1641 as part of a general rebellion, this was put down and in 1649 Cromwell arrived and Catholic land was confiscated etc (why we now have two Irelands) and in 1689 we had the Battle of the Boyne when William of Orange defeated the catholic King James II. It was a bad few years around Drogheda. This I think is the current Queens line. In 1496 Poynings Law ceded power to the Crown and I assume somewhere in all this Hugh De Lacy lost out but I am not a historian so check my understanding out for yourself but if you are on the De Lacy line you have some history here and should consider a professional researcher, there is a list of them on the National Library of Ireland site and I think also the Society of Irish Genealogists. Chuck DeLacy into the search engine here and get some history too. http://jbhall.clahs.ie/ The County Louth History Society have journals back to 1904 on JStor and if you want to check them a yearly subscription of about £15 will give you access but not sure how much DeLacy you will find, but as you can see the family were Barons etc back in the day, if you ever take it further let me know please and put it in the Chronicles section also as it is really an important name in Irihs history. Also have a look at your bridge