I've recently dealt with this type of account with DD, the issue we had was that her largely absent father was a joint trustee on the account so nothing could be done without his signature. With hindsight it should never have been set up that way in the first place, but obviously I didn't anticipate a divorce when dd was a baby.
I left it alone, with both of us still paying in until she reached 18, it's a fairly substantial amount of money but with interest rates so low and wanting as low risk investment as possible anyway it was preferable to leave it be. I certainly wouldn't have wanted him to take control of it.
DD opened a separate account in the meantime in her own name.
When dd turned 18 she asked her father to transfer it into her name, thankfully the bank was very helpful and allowed us to sign the paperwork separately, which he did eventually . So she now has control of the account, with my guidance.
Can you agree on a savings account you are both happy with that it could be left in until 18?
I would try to do that now if you're still communicating reasonable well. In my opinion a child savings account of that level of value should be managed conservatively .