1st trip to Ireland help with itinerary

I would for sure add Dingle to your itinerary..... We had 2 nights there and all really enjoyed it. Inch beach is near by and gorgeous. We also stopped at Derrynane Beach while driving the Ring of Kerry. Absolutely gorgeous. Just know that the Irish beaches are different than the beaches you are used to. The water is freezing. We were there at the end of July. My daughter went in but she was the only one. The Irish were wearing wet suits to swim!
We also really enjoyed Killarney. We biked in the National Park, went to Muckross House/farm and also took in a sheep sharing demonstration at Kissane farms. My kids were 8 and 11 and both loved it

If you're driving, drive through the Burren. It's on your way to/from the Cliffs of Mohr. While in the Burren visit the Ailwee Caves. Ireland is small country. Easy to drive around and see the non-touristy things. We found an obscure marker in the road to Bandon where Michael Collins was shot, a 300 year old woolen mill I can't remember where, a crystal factory just outside of Waterford. Stay in Bed & Breakfasts as much as possible preferably in smaller towns. Visit the local pubs. The Irish people are friendly and like to share their country. Enjoy your trip.

To answer a few of your specific questions:

"Cork 2 nights (with Glendalough on the way?)"
Glendalough for sure. The monastic site there is worth several hours. Although the Visitor Center doesn't open until 9:30 (along with access to the bathrooms) you can wander thru the site any time. An early arrival will get you there ahead of the crowds and get you on your way before the buses arrive.. Unless you have an ancestral connection to Cork I personally wouldn't recommend it - just too many other priorities for a 1st time visit. One of which is Kinsale just to the south.

"maybe 2/3 nights Kenmare"
good choice. Lots to see and do along the ROK and in Killarney NP without having to do battle with the tourist hordes.The Gap of Dunloe is beautiful (again, get there early). Your son might enjoy the trip out to the Skelligs.

"Stay in Kilkee? Killaloe? Lahinch?"
I'd say none of the above, but rather stop at the cliffs on your way to Galway from Dingle, which is always worth a couple of nights. Galway is central to the Connemara region - for our money the prettiest area in Ireland (which is saying plenty). The drive from Galway to Belfast takes about 4 hours. Suggest a stop in Derry (or Londonderry to the Brits) - one of the prettiest walled cities in Europe.

"Belfast 3 nights (Titanic museum, murals & Giants Causeway)"
Another good choice. Belfast is a fascinating place, and the Titanic Museum is really world-class. Could maybe shave a day there to visit Newgrange and the Boyne Valley heading towards Dublin from Belfast. Lots of Irish history in a compact area.

"We're from So.California and are hoping for some beach"
Though Ireland isn't exactly a beach destination, the broad expanse of Inch Beach near Dingle is quite nice. Believe they do surf there...though seasonally.

Safe travels

I would also skip Cork and go to Kinsale as another person suggested. Kinsale has Charles Fort on one side of the harbour (interesting walking tour), and the ruins of James Fort on the other side of the harbour (I took a picnic lunch out here and had the place to myself). I would also suggest stopping in the Killarney area, if not the town itself then at least the park or one of the other sights. After that then the Dingle area would be a good choice. From Dingle the Cliffs and the Burren are on the way to Galway. Galway would be the place to spend a couple of nights. Lots of things to see and do from there, and the drive to Belfast won't be too long.

Thanks for the input...

So we've changed up to 2 nights in Kenmare, 2 in Dingle and 2 in Galway before driving to Belfast.

How long is the drive from Kenmare to Dingle? Dingle to Galway? (with cliffs breaking it up)

Wondering if we should shave a night off of DIngle to have a stop between Dingle and Galway?

Thoughts?

and as for beach, I just meant that we love the ocean...not thinking about swimming.

For drive times we use Google maps, though there are other sites available on line. The street view feature is handy for previewing specific routes, signage, roundabouts, etc.
Most here on the forum would advise adding time to that quoted on Google maps to account for the more relaxed flow of traffic in Ireland...especially in the rural areas.
Kenmare - Dingle takes less than 2 hours, longer if you take the scenic route clockwise around the ROK, which we recommend. There's a pretty spur called the Skellig Ring Road that is worth a detour - will take you to Portmagee and the Skellig Center along a road free of tour buses.
Dingle - Galway takes barely 4 hours as a straight shot, longer of course if you include the side trip to the Cliffs and the Burren. The faster route is via the new motorway near Limerick, though personally we prefer the more scenic drive via the Tarbert ferry up thru Kilkee and Kilrush. Lots of pretty ocean views that way...if the weather cooperates.

As far as google maps goes....we found its was grossly under estimating the road conditions. Our fault, like many in Ireland, was packing in too much driving for our time there. We headed immediately to Glendalough for some hiking after our red-eye from the east coast and went from there to Kilkenny with our Dublin experience on the backend. We did go to Cork for one night on the way to Kinsale/Dingle.....we liked the Queen Ann's market, the church bell and University....but our option may skewed because they were having torrential rains and flooding when we were there in 2013 so for me a skip on this would be ok. We liked....loved...Dingle (and the loop drive there-Slea Head Drive) better then the Ring of Kerry and wish we had spent more time there. I will third/forth....Kinsale. We LOVED it. Our B & B was amazing and the food there was perfect. Galway a lot of people love but I would have rather had an extra day in Dublin!

In northern ireland, add the carrick a rede bridge. You did not ask about accomodations, but many mid priced hotels offer a double bed & a twin, and a fairly authenti breakfast buffet