Tell our ISS allies the space station will be finished once the HLV is operational. The shuttle is just not going to get the job done. As for the 3 modules that are designed for only the shuttle to bring to the ISS, Zubrin mentions building some kind of space tug to get them to the station once in orbit. This is probably the best way to go.

Another option, albeit an expensive one, might be once the CEV is operational launch it along with an unmanned shuttle carrying the ISS modules, and once safely in orbit transfer the crew over to the shuttle and fly it to the ISS. This is similar to what will be done with a lunar transfer vehicle anyway right? Then transfer them back to the CEV if there is tile damage or have them land it if not.

Either way, end shuttle flights now and move that money to making the HLV. Once the HLV is online finish the ISS quickly and safely with unmanned heavy launches along with manned CEVs.