Do you live in Wales and/or are any of you Welsh? North Wales is massively Welsh speaking and you will absolutely need to learn it to properly live there, because, if you've done even basic research, you would know how many locals make up the numbers in tourism. And more importantly, how hard it is to integrate without the language. And how proud people are of their culture.
Having (grand)kids? of school age, they will most likely also need to immediately start to learn Welsh, as a huge percentage of schools are Welsh-medium. Have you looked at further educational and job prospects for your grandkids growing up there? It's, generalising, not good. They probably wouldn't want to work at the campsite and also wouldn't have the freedom to go and do much at the weekends if you're all busy, which could become a point of serious friction between you all. Not to even mention the men trying to work full time as well (they will inevitably be roped in on the campsite, by necessity). Issues galore there too.
Local planning permission is a nightmare. That will probably end your dream at hurdle one, tbf. The new council tax rules/minimum occupancy/tourist tax/general death of the market/incompetence and purposeful obfuscation from planners will all fuck you, hard. ...especially if you're not Welsh. People will moan at this statement but it's true. Don't lose your pension, is all I'm saying.
Tradesmen are basically impossible to pin down in North Wales, the cost of building materials and labour are tenfold what it all was pre-covid, and again tradesmen will prioritise Welsh speaking jobs... Rightly or wrongly. As will literally anyone else you deal with (for supplies, cleaning staff, whatever). Your set up costs will be absolutely shocking, once it's all laid out, from ground work, cabins, parking area, utilities being put in, insurance, stock and septic tank pumping and general maintenance and and and...
The weather is very wet and shit and eats away at even expensive wooden cabins. Occupancy could/will be for a small portion of the year only.
if you and DIL are the only people keeping it running including constant year round maintenance, well, I hope you're hardy. And get on exceptionally well. And are not near a river or any form of water (hint, everywhere has a stream nearby and may or may not flood lol). The wind is shocking . The drive from England puts people off. Did I mention the rain? 😂
Sorry to be so negative. But the glamping scene is a money pit in rven slightly adverse circumstances, and legislation and so on in North Wales is increasingly pointing against profit. Put chatGPT down and seek some more real advice!