@Parsley65 you can easily do low carb with your DC - they don't need massive/frequent portions of carbs either! That said, while their diet could be lower carb it doesn't need to be low carb, as would yours be if you're aiming to lose weight.
There's no need to cook different things. If you go and have a look at the recipe threads (all stickied at the top of the Low Carb Bootcamp topic) you'll find loads of stuff that's all perfectly family-friendly.
Equally, you can simply add carbs to your DC's meals. So say, for example, you're cooking something like a roast chicken - you add roast potatoes to their plate but not to yours. The rest of the veg is lower carb, e.g. broccoli, cabbage, leeks, cauliflower with a cheese sauce (made with cream rather than flour so it's low carb), etc. But the core of the meal is the same for all you.
It also doesn't need to be more expensive as you would be, essentially, cooking the same meals as you were before, just with less of the carbohydrate element.
If, though, you have been relying on lots of meals based around pasta and rice, then this would mean cooking two different meals - unless you switch your meals. Again, though, there's an alternative - you can buy low carb/calorie noodles (Bare Naked Noodles - widely available in supermarkets) which you could use for you and DH, whereas the DC have normal pasta. These aren't cheap though. In which case, look to substitute pasta for veg - spiralised courgettes, or thinly sliced cabbage make great alternatives to spaghetti. Or you simply go without - when I make chilli these days, we don't bother with rice, but top the chilli with grated cheese, jalapeños and sour cream.