Fly and hire a car, OP..!
We do the drive a couple of times a year to do longer holidays with family, and it’s a pain
The roads to Holyhead and Stranraer are both mostly single carriageway lorry routes, so you mostly crawl along at 40mph behind a fleet of HGVs
Neither Irish ferries nor Stena use particularly modern boats on that route so the cabins are pretty bleak, and there isn’t much else to do on board
We got lucky one Christmas when they used a boat normally on the Ireland to France route, and it had a cinema and soft play area but I haven’t seen it since..!
Getting on and off the boat can take an age, and even if it doesn’t, it’s still a really slow journey
We only drive when we have to go with our dogs, and I really dread it
Flying is so much easier, quicker and less stressful, and you can take a buggy and car seat for free as part of the child ticket