Ref. No. 1431/42-860
In the name of Allah, the most Gracious the most Merciful
The answer to your question is as follows:
The reward of charity is for the one who gives charity. However, at the time of giving a charity you have the intention that you are giving it on behalf of your wife then she will be rewarded for it. Therefore, while giving alms, make the intention that you are giving some Sadaqa on your own behalf and some sadaqa on the behalf of your wife, so that both may be rewarded.
And Allah knows best
Darul Uloom Waqf Deoband