How exciting that you are planning a trip to Ireland soon. I can completely appreciate why you would feel a little nervous about driving here in Ireland. We are a tour operator providing transport for small and large groups and designing customized itineraries for Ireland! Your route sounds really nice and we'd be delighted to help you organise your trip.
One option would be to have a private driver-guide throughout your trip (starting in Dublin travelling to Killarney, Ashford, Galway and ending in Dublin). You could see places like the Ring of Kerry, Cliffs of Moher and Connemara with your own local expert. Having a private driver-guide also lets you veer off the beaten path and see little hidden gems. I'm attaching a sample itinerary to give you an impression of what we do: https://www.special-ireland.com/packages/irish-castle-and-manor-vacation/
Just to let you know that our online itineraries usually include accommodation in the pricing but if you've already booked accommodation, we also do transport only itineraries.
Another option would be to have a mix of rail and private driver-guide, as this is more economical and could be fun! We have a sample itinerary which can be tailored around your preferences: https://www.special-ireland.com/packages/irish-explorer/
I hope you find this useful and if you have any questions just send us a message :)
Thanks and all the best,
Deirdre-Specialized Travel Services