I was traveling alone to the UK 2 months ago, and my visa is still valid (6 months). Now, for the second time, I want to travel with my wife and daughter, but I wrote in my form, my dependent people will not travel with me to the UK. Can I request a visa now for my family and go to the UK with them? What should I write in my wife and daughter's form for this question: "How much do you want to spend on your travel to the UK"?
You have a valid visa and, with that, you're able to travel to the UK. For your wife and daughter to accompany you, they need to apply for their own visas. As part of her application, your wife will be asked about her partner, you, and for your information, including your passport number.
If you are the one underwriting the trip for the whole family, your wife would identify you as that person and include your financial documents showing that there are sufficient funds available, just as you did in your visa application.
You might want to review the UKVI guide to supporting documents to make sure you have all your bases covered, before submitting their applications.