You may struggle to find any documentary records for this family. Raloo Presbyterian church has no records before 1842 and the Non-Subscribing Presbyterian church has none before 1859. If the family was Church of Ireland then their early records were lost in the 1922 fire in Dublin.
Griffiths Valuation for Raloo, compiled in 1861 has about 35 McDowell households listed in Raloo. http://www.askaboutireland.ie/griffith-valuation/index.xml
In the tithe applotment records for 1830 there were 19 McDowell farms. The name is spelled Medole there, which reflects the local pronunciation of the name in Ireland. (It is still pronounced that way here today).
The tithes only listed folk with land ie mainly farmers. Labourers, shoemakers and others without land would not normally be listed there. All the tithes really do is tell you where there were farmers of that name in Raloo in 1830.