Not read all the others, but as ive done a lot myself:
Its a lot like cycling. The poorest equipment will make you hate it and never go again.
You DONT have to spend a fortune, just be careful what you do buy.
self inflating mattresses are one of the biggest advances in camping this century imo. Aldi have them in at the moment for naff all. The aldi ones are heavy, but if you are car camping that doesn’t matter one jot. I would choose a thinner self inflater over an airbed every day. Much more comfortable despite being thinner
I imagine you kids would love to have “their own” tent. So two smaller ones might be more fun, but depends if you are happy leaving them out on their own (a few meters away with half a mm of nylon between you) overnight.
You can get big ol’ glamping wigwams for a not too much now.
Where are you? we can recommend some killer great sites if you are thinking of heading daaannn saaaf.