I have been to county Kerry several times but not this late in season..October 18 to 31..what should I expect and should I tell my first time Ireland travel companion not the"right" time to see Kerry for the first time
Next to impossible to predict the weather this far out, other than it's unlikely to be extremely hot or cold. A bigger issue for sightseeing is the length of daylight: it will be dark around 6pm-6:30pm, earlier if it's a very cloudy day. Once the clocks go back on the 29th, it'll get dark around 5pm. You'll have a shorter time to see stuff, but more time to visit the pub in the evening.
You should tell your travel companion that a Guinness can cure a rainy day 9 out of 10 times. (Sometimes two are needed.)