As mentioned above it's bizarre how Kayleigh is a disapproved MN name but Eilidh isn't (exactly the same name but without the K!)
Really, what is this MN disapproval of K names?!
You're extrapolating wildly. Eilidh is hardly regularly discussed! And I'd wager that MN is split into 4 groups regarding it, -a) those that haven't heard of it/can't pronounce it, b) those that don't like it, c) those that don't like it, but wouldn't say so, for fear of offending another culture, and d) those that do like it. In fact most people probably fall into a mix of those categories.
Kayleigh on the other hand is easily read/pronounced by the majority, also a lot more people will personally have met one/some and so formed judgements that way.
It's not a 'K' issue- after all names like Katherine, Kate, Kiera... Are not universally disliked. It's a class issue.
I prefer 'classless' names, like the OP's son 'Ben' he would fit in anywhere he wants to be, and I think that is useful to anyone.