The P226 mags will work in a P228/P229 of the same caliber (P228 is 9mm only). The only issue would be that the P226 mag will stick out slightly from the bottom of the P229 grip. This can be mitigated with an X-Grip baseplate adapter if you like but is merely a cosmetic thing. If it doesn't bother you, don't worry about it.
The geometry angle and release notch are identical between them.