It makes sense for you to share your tax credits in such a way that you minimize the tax payable. This would mean you assigning some of your tax credit to your husband.
The other suggestion that he use all the tax credit will mean that your take home pay will drop.
If you both put all your income into a joint account and take from it as you like and have a similar attitude to managing the household finances, when it doesn't matter where the tax credits are assigned.
But .....if you have not worked out these issues in your relationship, then him having control of what is effectively your pay could cause a problem, if you are uncomfortable about this. You dont say if you lived together before getting married, but I dont know if you have already talked about these things.
Control over money causes a lot of relationship problems.
Also, you say that you will try to have a child soon,
Lets say that you start trying to get pregnant in 1 year and it takes 9 months to get pregnant, and then you work for another 8 months.
That is 2.5 yrs before you have to deal with being a single income family.
Changing your tax credits takes about 30 seconds, there is no reason for doing it now " to save messing later on".
I would sort out the more fundamental issues about money in your relationship and then the issue will be easy to resolve.