The SC-2345 is good for your accelerometers, and the SC-2040 is an option for achieving simultaneous-like sampling with sample and hold circuitry, but I don't think you can use them together. Do your samples have to be truely simultaneous? The PCI-6013 has a maximum convert clock rate (the clock that switches between channels) of 200kHz. So your samples would be only 5 micro seconds apart. Is that too much? Otherwise, to get truely simultaneous accelerometer samples, you are probably looking at an SCXI solution (which can't be used with B Series, like the 6013) or a simultaneous multifunction DAQ board (S Series).
-Alan A.