Holly's child benefit goes into her trust fund, along with any money she is given for Xmas/birthday etc, in the hope that when she turns 18 she will have a nice big lump to go to uni, see the world, buy a car, deposit for a house....although I'm hoping she will use it for uni.
Once there is about 4k in her trust fund, I am going to open a separate account in my name for her - so that if she is like me at 18, she can't blow the whole lot!
I save quite a lot for her/us at the moment, so that if we have a rainy day, or if I am ill and can't work (I'm self employed), we have a buffer.
I don't think anybody should feel guilty if they spend the child benefit or tax credits - you live as a family, therefore the money coming into the household is for the family. Whether it goes into a savings acc, or on nappies, or on food, or on bills, or activities, makes no difference.