Can you give us an idea of how far you're riding each day, the elevation gain and the speed? I like my Creo, but it just doesn't have the power of the Domane HP+. If you're doing an average of say 28 km/hr. or slower and say 100 km's a day then the Creo will likely be ok. But if the group is going to be doing say 33 km/hr. then I'm not sure the Creo battery will be enough. I think the Domane HP+ can be had in a dual battery configuration if that's what you need.
I guess it also depends upon how much power you're supplying. When you ride your Santa Cruz do you know what your FTP is and your watts/kg? What about the group in general? That would help understand how much power you need to keep up with the group. If the difference is small then the Creo will likely be fine, but the bigger that gap the more likely you'll want the Domane HP+.