Last leg of Europe travel, UK to Dublin or southern city for 3 days

Hi, my 21yo and 19yo children are in Europe exploring and will be meeting my mother in law in London for 8 days. She lives in the US, but was raised in London so they will be primary based out of London, but it was $400 cheaper PP to fly out of Dublin on the way home so the plan is to fly over to Ireland on a Monday morning flight, and then they fly home on Thursday at 2:30. So a 1/2 day on Monday, and then 2 full days. Any thoughts on flying into a city that’s more south, seeing a little countryside staying over night 1 possibly 2 night and then getting to Dublin sometime late on Tuesday or Wednesday morning? Or is it best to just stay in Dublin and take full day tour south to certain sites? My kids will have just traveled across Europe for 5 weeks, so they will be fine navigating transportation, and my mother in law is very active and so should do fine with a few long days. I’m sure my kids money will be running low by the end of this so I may have to pitch in for this last leg, so if I can avoid those expensive tours great, but if it’s the best use of time that’s fine. I also would prefer they don’t get a car since they are 21 & 20 and my mother in law is too anxious to drive, but if it’s the only feasible way, and they rent to 20 year olds I would consider it.