Dag Eva,
It's great that your itinerary is shaping up so nicely! You can either go over land (and Limerick), or take the ferry.
Both routes, taking either the ferry or going around, are lovely to take and the time difference between the two isn't that great, so if you enjoy ferries I'd go for the ferry. :)
If you take the land route over Limerick, one of the places you'll pass is Castleisland, which is the home of
Crag Cave, an amazing place to visit; an ancient fossil cave system, older than mankind itself. In Limerick itself you will find the starting and ending point of
The Limerick Drive, which is quite a lovely route to follow, and you can choose to do parts of it as you travel towards Spanish Point.
If you're going over the ferry, the
Farmer's Market in Listowel (if you're there on a Friday) or
Listowel Castle are two great places to stop off.
And I'm sure some of our community members along the route will have some suggestions for you too.
Een hele fijne dag,
Cornelia