Investments for grand children

Oops sorry, I totally misread the op. It was slightly confusing, that's my excuse
Mum had her savings in my name to protect her benefits but if you don't want them to know I don't know what you can do.

Could you not open children's accounts and have the pass book in your possession?
That way your children won't know how much is in the accounts. I believe you can set up accounts that your grandchildren can access at 18 or something similar.