Giving Tzedaka via CC is not lechatchila at all. the mitzva of givingTzedaks is fulfilled by giving cash or cash equivalents, like a check. A CC is most probably only giving money through the mechanism of Eved Kenani, definitely problematic for matanos laevyonim/ kiddushei isha and not a maasheh nissinas tzedaksh at all.
Of course YMMV
Since when is a check considered cash equivalent?
I once heard a shailah - regarding the halachah that you have to pay a worker the same day, if a check is considered payment. -
Many times the person can't cash the check bec the bank is closed, or bec they don't have ID, etc
Regarding maatonos le'evyonim, I believe most poskim hold that you need to give cash. (unless you're giving to an organization that's going to distribute it for you then maybe its different? I don't know if the psak that I'm referring to applies to organizations)