I’m not really a hedgehog expert but I have been researching them for ages now and know quit a bit about them.
I think the best thing that you can do is just carry on putting food and water out, you could also get some mealworms which will be really nutritious for them and put them out with the cat food you have already.
A good tip I would recommend is that when it is getting dark is to just give your garden a good water and the grass so that when the hoglets come out in around 3- 4 weeks there will be more insects such as slugs coming out that they can eat. Another good tip that I do sometimes is get some soil or compost In a heap and spray it thoroughly with water as this will attract things like slugs into it and the hoglets and mum can forage through it for them. It is also brilliant if you have a pond because they will attract small, insects even if it just a washing up bowl.
hope I could hep you