All the high density dielectrics behave pretty similarly w.r.t. DC bias voltage and capacitance. If it's a 1210 cap, it will be about 3uF at 30V, a 1206, 2ish uF, 0805 as low as 1uF.
I disagree. I wanted 10 uF at 25V for a board I was working on recently. I was looking exclusively at 1206 caps, and found that they ranged from around 3uF to barely 1 uF at 25V. I also found that most data sheets do not include this information.
Keep in mind that X7R does not denote a type of ceramic, nor any characteristic of a ceramic except capacitance vs. temperature. Any ceramic that meets the X7R temperature characteristics can be called X7R. And they do vary substantially from one manufacturer to another, maybe even from one line to another.
I ended up using tantalum polymer, as they exhibit far less variation with bias. I ended up with substantially less board real estate for 10 uF at 25V than I could have with ceramic.
If you find this topic interesting, Maxim's app note 5527 is very informative.
To the OP's question, if the driver specs a 25V part, then you probably shouldn't put 30V on the driver. If the driver is designed for 30V, it should have a 35 or 50V part on it. If you are talking about a brief transient at powerup or something like that, it's probably fine.