Help with 14 day Itinerary

Have you considered flying into Dublin and out of somewhere in Belgium or maybe Amsterdam? Airlines have something called ‘multi-city’ or ‘open jaw’ flights, generally under their Advanced settings.

You only have 14 days and it appears that you wish to spend a lot of time traveling.
Flying from Ireland to Amsterdam, then to a beach somewhere?

At some point going to Belgium.
Then back to Dublin.

I have traveled quite a lot in my 76 years and have learned to pace my travels to avoid unnecessary travel, especially flying within Europe. You waste a lot of time going to airports, waiting for your flights then arriving at another airport, getting you luggage, etc.

Also, if you visit a place like Ireland, it deserves several days. I suggest at least a week. Dublin is great and worth 2-3 days minimum.
Going to the scenic SW coast is a great idea, but suggest planning exactly where you wish to go. The Ring of Kerry is nice, as is the Dingle Peninsula.
https://www.ireland.com/en-us/destinations/regions/ring-of-kerry/

You could spend the entire two weeks in Ireland visiting N. Ireland as well. If you still wish to visit another country, then consider Great Britain, Wales, England and Scotland. Scotland is nice and you could do another week there. England and Wales are great, we did a trip there a few years ago and spend FOUR weeks there and didn't see it all.

We recently spent a week in Amsterdam, you could do that great city, suggest at least 3-4 days. Visit the Amazing Rijksmuseum and Anne Frank House.
Belgum is close to Netherlands and you could take in Brugges, a well preserved old city.

As for beaches, I suggest making the most of Europe's scenic places as well as historic and cultural landmarks. Beaches in Florida or California are better than most of Europe. Of course, the Greek Islands are great, but that is another story.

Suggest doing research, check out TripAdvisor for things to do in cities.
Also, you can fly using an open jaw ticket. Fly into one city and then fly out of another. For example, you could fly to Dublin, then visit Ireland and England, then fly out of London.

Thank you everyone for your suggestions and will consider as we finalize our trip. I have not heard of jaw ticket but will definitely look into it.
Karey

There are beaches in Belgium but I don't know if they are rocky or sandy or if the water is warm. But if you post on the Belgium page, someone could probably tell you more.

I've walked on a beach in Belgium, near Dunkirk. I think it was sandy, but that far north, the water may be cold even in Sept. And having been to all of the above, I think that is too many different places. At most, Dublin, western Ireland and Amsterdam and fly home from Amsterdam. You could also consider flying into Shannon and seeing the west coast of Ireland before going to Dublin. Every time you change locations, you will lose the better part of the day.

Great recommendations and will shorten the number of stops.

Beaches in Belgium and The Netherlands are sandy and the water won't be warm. Zandvoort (ironically called Amsterdam beach by the Amsterdam tourist board) and Bloemendaal aan Zee are west of Amsterdam and Haarlem, and reachable by train. When staying in Haarlem, just cycle to the beach so maybe you can combine Haarlem/Amsterdam and the beach this way. https://www.visitzandvoort.com gives a feel. There are quieter areas along the North Sea coast and maybe you want to consider the Wadden Islands (i.e., Texel, Ameland, Terschelling, Vlieland and Schiermonnikoogg) in the north. It will be post local holiday season so you may have better availability. Don't expect Mediterranean Sea or US beach resorts and hotels. You may be disappointed, so really check whether it is up your expectations.