Congratulation for the great news!!!
If I will be you, I will use part of Bitcoin to cover first expenses you will have soon.
For the rest, I will open separate account- wallet and keep this Bitcoin for child.
In 18 years this can be huge value and maybe pay for his tuition at college, new house, car
Nice advice of yours, I think she will follow your opinion it is like you save money for time deposit then after several years, you will take the lump sum of your fruit of labor which is the harvest time in the right time of course.