Nice clean campsites in Northern Ireland

Belfast

Giants Causeway

Those 2 might ft the bill. If not then there are others on:

https://www.ukcampsite.co.uk/sites

Not had personal experience of above sites but did make a pre Covid list for a visit. Still getting there!

Places to go? - a copy of the guide book in the photo will be invaluable.

Stopover sites?  Trawl all the websites -CamperContact, Search for Sites, UKCampsite, ACSI Eurocampings, etc.

No personal experience either as I I only went to Killarney in the far south west.Let us know how you get on.

It's 6 years since we last visited Northern Ireland but we stayed at these sites and found them to be excellent:

Feigh Farm CL which is less than 3 miles from the Giant's Causeway and has views over to Rathlin Island. The owners were very friendly. Toilet/shower and washing up facilities were fine. There was a charge for the shower.

Cusher Valley CL not far from Armagh. At the time I did a review and I thought it was the best CL we had ever stayed on (with Feigh Farm a close second). The toilet/shower block was excellent.

Delamomt Country Park Camping and Caravanning Club site - almost on the shores of Strangford Lough -usual CCC standard  It is about 4 miles from Downpatrick which is worth visiting.

A few years earlier for visiting Belfast we stayed at Jordanstown Loughshore Park . It is at the side of Belfast Lough and is Council owned and run. There are buses from near the site to Belfast. We too are seniors and found it no problem to walk  the half mile or so to the bus stop near the  Spar shop in Whiteabbey. It was a pleasant walk along the seafront and from what i remember there were more frequent buses from there than on the main Shore Road stop nearer to the site. There is a public carpark/cafe and children's playground by the campsite but there were no problems with these.Do check out the website and book in advance because the campsite manager/warden is not always on site and a code was given by the council in order to initially access the site. We found it to be an excellent base for visiting Belfast and  a pleasant outlook across the lough as did friends who later stayed there on our recommendation.