Start making a list and collect stuff as you go along until next year you're ready to set off. Don't forget the simple things like water containers, bowls for washing and washing up, a little bottle of washing up liquid (I use a small contact lens solution bottle) etc. I have three double burner stoves, gas, meths and multifuel. The multifuel wins hands down for power and usability but even with that the flame is a bit feeble so if you use it in windy conditions it needs shelter. Paraffin and petrol can be dirty and smelly, gas and meths are extremely clean, gas is very convenient but you always need a spare cylinder. All can be dangerous, gas can be very dangerous in an enclosed space, meths can be dangerous because you can't see the flame, petrol can ignite from a spark several yards away. If you use gas for family camping don't be tempted by the little pint-sized gas cannisters, get a stove that can take something like a 4.5kg bottle. Most of the time I only take a single 'roarer' burner petrol stove with me when I camp, it will cook in a gale on top of a snow-covered mountain. You probably won't need that sort of performance for your first few trips at least but if you come across something like that which runs on petrol or paraffin in a boot sale it might be useful as a backup. They're expensive to buy new, usually over 100 quid.
Yeoman Outdoor have a
list of their shows on their Website but unfortunately the last one this year finisheS on 27th September and it's in Darley Dale, very near me as it happens. Their displays have dozens of all kinds of tents from one-man lightweight to things as big as a house, all erected in a field so you can see them. It would probably be a good idea to see that. They do some cheap tents and they sell the display examples off at the end of the show. Tents tend to get expensive when they are very light, for backpacking. You probably don't need to worry about the weight if you're using a vehicle so you can aim cheaper. I actually prefer the groundsheets in the cheaper tents as they're that bit heavier and I think a bit tougher. I have several very cheap tents, some of which I've bought from Yeoman, and I'm happy with all of them. I have an expensive lightweight tent and I don't like it at all. If you're going to have a camp fire give serious thought to getting a canvas tent, it's less likely to be holed by hot flying embers and safer in my opinion, especially with kids around. It will be heavier, especially when wet, and will need more care.
You'll sometimes be very glad of wind breaks and a porch, awning or tarpaulin. Of course you might be heading off to southern Spain and things might be different but it will be a longer trip.
Gotta do some work now, sorry...