Maybe Tom.
"In 1894, at his own expense, Alexander Shaw invited the celebrated Scottish golfer, Old Tom Morris, to Lahinch to have a look at the course and suggest improvements. Tom Morris was deeply impressed by the natural golfing terrain and by the sandhills. In his construction of the new course he placed great emphasis on the Sandhills side of the Links. He said, when his proposed changes were implemented, Lahinch would be on a par with the five great Links courses of the United Kingdom."
Just as it appears the course was laid out by Shaw and Plummer (not McKenna)
"On 26th March 1892, Alexander W. Shaw and Richard J. Plummer, two prominent officials of the Limerick Golf Club, went to the West coast of Clare as a result of a casual rumour that, somewhere between Ennistymon and Miltown Malbay, there was suitable ground for a golf course. While travelling from Ennistymon they passed what was then a dreary desolate piece of land, a mass of sandhills. Struck with the possibility that the land was suitable for a golf course they stopped and made enquiries. The result was a second journey on 9th April when an eighteen-hole course was marked out. E. D. Hunt, a colleague from Limerick, accompanied A.W. Shaw and R.J. Plummer on their second visit. They were helped in the laying out of the course by some officers of the Black Watch Regiment who were stationed in Limerick at that time"
Seeing as this is taken from the Clare Journal of 11th April 1892, I have no reason to not trust it.
Also, with reference to McKenna and another to Old Tom:
"James McKenna came to Lahinch on 1st April 1893 and was employed as the first Professional. His wages were 18/- a week, 2/- a round for instruction and 1/6 to play a round. All members contributed financially to help retain his services. His arrival predated the coming of Old Tom Morris by over a year. It is clear that it was McKenna, between 1894 and 1899, who supervised the changes and improvements recommended by the great Scottish golfer"