Traveling whilst Pregnant - Logistic Questions about Dingle Peninsula

I wouldn't rely on GPS or any electronic device to find my way about the country easily or accurately, especially given your condition and the need to stop when, well, the need arises.

Get Michelin map #712, which is quite detailed and shows all the major and minor roads and much more. From Doolin, head southeast to Ennis then southwesterly to Killimer, where you can take the Killimer-Tarbert ferrry into Co. Kerry. Alternatively, from Doolin you can drive along the coast to Lahinch and Kilkee, then head east to Killimer.

The ferry has restrooms aboard and a small shop selling refreshments. It'll save you a lot of driving. Here's the link:

https://www.wildatlanticwayonline.com/clare-limerick-wild-atlantic-way/discovery-points/killimer-tarbert-ferry/

From Tarbert, go south to Listowel and Tralee then southwest to Dingle Town. Et voila!

You can pop into any pub or restaurant along the way for restroom stops.

For B&Bs accommodations, of which there are many grand choices, check these links:

https://d5qsyj6vaeh11.cloudfront.net/files/brochures/pdf/english/AC20ENG101BBD---Bed-and-Breakfast-Ireland-NEW-637141676027212373.pdf

https://www.bandbireland.com/

Here's the link for Slea Head. I'm not sure what you mean by making the drive as short or long as you want. There are several villages with many B&Bs on that end of the peninsula.

https://dingle-peninsula.ie/explore/slea-head-drive.html

Slainte and gute Reise!

We've always had good luck using Google maps while driving around Ireland. There is a fairly straightforward way to download maps and activate the navigation function without eating up all of your data. Can probably search on the forum for instructions on how to do so, or alternatively PM me and I can walk you thru it. I do agree that having a detailed paper map is good to have.
Heading down thru Ennis, Limerick, and then along the N-21 to Dingle is probably the most direct route if you just want to "get there", but the prettier way to go is down the coast to Kilkee and then over to the Tarbert ferry landing at Killimer as previously described. A lot will depend on the weather - if it's a sunny day the route via Kilkee is worth going a little out of your way for.
The ferry is first come, first served and departs every half hour as I recall so you'll want to crank that into your planning.
Public restrooms are something you'll usually only find in some of the larger villages, but petrol stations, tea rooms, pubs, etc. are all handy as needed.
The Slea Head Drive loop is only about 35 miles around, so you could (I suppose) race around it in an hour, but you really don't want to do that. There are plenty of places for a quick pit stop so I wouldn't necessarily curtail your enjoyment of the experience due to that sort of concern. We're seniors who make it a point to never pass up a restroom ourselves, and we've never had any issues along the loop. I think you'll be fine too.

Weather in Ireland can be tricky. If it's raining, the Slea Head Drive will be miserable. If possible, I'd book two nights in Dingle to give you more options regarding the weather. Dingle is a fantastic town with an amazing music scene. You won't regret spending some time there.