Just to redress the balance of facts here (off-topic, sorry OP), extra accounts for a DC/DGC can be a good way to save tax-efficiently for a child's future.
You can have a trust fund but can only put up to a certain amount per year into one. Once you get past that limit, there are special higher-interest accounts for children which can be useful (we have one with the Halifax) and also, as I mentioned earlier, pensions. Grandparents can (so I've been told) also set up accounts for grandchildren as a tax-efficient way to avoid inheritance tax in some circumstances.
Sorry to deviate from the subject, but I did just want to correct some of the things that have been said here.
Of course, the multiple accounts and accounts by GPs would be of no use to the OP if she doesn't trust her MIL.
But for others, they can be good ways to save.
For what its worth, my DD's Child Trust Fund says the money cannot be withdrawn by anyone until she is aged 18. And the money is then paid to her, no one else.
Financial Advisor told us that if we wanted to have control of the money (to stop DD spending it on something we didn't want her to) then we should just pay money into an ISA.