We have been trying to determine if we can realistically make a day trip from our hotel in Ennis to Dingle in a day. Have seen posts on various forums about using the ferry to bypass the drive through Limerick (especially since we will be in Ennis and traveling around the area for a day or two already).
Also, in the ferry advertisement's, there are mentions of the ferry ride being short time to cross, possibility of seeing dolphins, etc. Is the ferry ride pleasant, especially would it be for our 6 and 8 year old grandsons?
All in all, trying to not have to move hotels, staying in Ennis, but be able to enjoy at least some of the “Wild Atlantic Way”.
The drive from Ennis to Dingle is pretty straightforward and can easily be done in less than 4 hours if you opt for the more direct route via Limerick.
If it's a sunny day, and if you're up for a more off-the-beaten-path excursion, then consider going a little out of your way and heading over to Lahinch. From there you can pick up the N67 down a very picturesque section of the coast to Kilkee - a pleasant seaside community featuring a broad section of sandy beach that the kids might enjoy romping on. There's also a very pretty cliff walk that we frankly like better than Moher - not least because we usually have it all to ourselves. Kilkee would also be a good stop for lunch, a cup of coffee, or just to pick up the makings of a picnic lunch for the cliff walk. The Tarbert ferry is a short drive away. It's first come, first served as I recall and only takes about 15 minutes to cross the Shannon.
From there the drive down to Dingle is via the N69 to the pleasant market town of Tralee - another potential stop to stretch your legs or to grab a coffee.
The more direct route into Dingle from there is the N86. For an element of adventure you could swing around to the north and come into Dingle via the Conor Pass, but I'd only tackle that on a sunny day and only after you've previewed the route by looking at the street view feature on Google Maps. The road thru the pass is pretty narrow in places and occasionally necks down to a single lane, so it can be a white knuckle experience for the uninitiated. It's gorgeous though and is worth the detour if you're game.
Edited to add in case I misunderstood your intent: If you were asking about making it to Dingle and back as a day trip from Ennis I'd say it's probably not feasible - that would make for a very long day indeed. Also, as pleasant as the ferry crossing is I wouldn't necessarily go that far out of my way for it. The drive down to Kilkee might be a pleasant day trip from Ennis however, and the drive around the little peninsula just to the south of there is quite pretty, features numerous little pull-offs to view and walk along the cliffs, and is way, way off the usual tourist track. Would be a good look at a part of the Wild Atlantic Way that most never see. There's even a little lighthouse at the tip of the peninsula that's worth exploring if you get that far.