Hi. I can't help but wonder if the Smith family you mention wasn't related to the Wm. Smith & Agnes Alexander family (married abt 1750) of Irvine. Children: Alexander 1752, Margaret 1754, Alexander 1758, William 1760, and Margaret 1761. Alexander 1758 later married Marion Jamieson and moved to Dundonald.
If I recall correctly, there was an Orr family in Irvine during that 1750-1800 time. Let me check and I'll get back to this thread if i find anything worthwhile.