If you're a first time camper then you don't want to spend much on camping gear, especially when you might not like it. On a sunshiny day, few things are better than an evening outside the tent, but if you're unfortunate and the hail comes in horizontally from the west, I'm willing to bet you won't be going again.
I recommend giving it a try on the cheap before you fork out too much. Here's a few options.
Buying a Tent
If you're an average family (if there is such a thing) and have a couple of kids then you would think a 4 person tent would be good enough. Think again. A four person tent is design to fit four people lying on their backs on regulation sized sleeping mats. That's not your family. You need a bit of room so I would recommend at least a 5 or even a 6 person tent. Look at the next section and you'll understand why.
Air beds take up a lot of room but I recommend you get some because a weekend of no sleep could be the end of your camping dreams. Forget about the foam mats, they are just torture, get one double air bed (if you're on speaking terms) and two singles, you won't regret it.
If you're camping in the summer you'll be able to get by with two season sleeping bags which are fairly cheap. Take some thermals and a blanket just in case.
Those kids need grub. You could take them to the pub but if you want to save a bit then invest in a stove. All you need is a single burner and some butane gas and that'll sort out all the meals. Get some bacon, some sausages and any other meat product you can think of and off you go.
Forget about pots and pans just dig into the back of your cupboards and grab some old stuff. All you need is a pan, a frying pan, knives, forks and a few cups and you're ready to go. Buy a big bottle of water and some washing up liquid on the way.
Other gear you might need from the house
Don't forget some soap for your pits and your toothbrush and towel. Toilet roll is useful I find. If you have torches take them along. Grab some warm clothes just in case and that's it. Hope you enjoy it.