One thing to remember is the more water flow you have going to it, the more cfm's and water lift you will need.
I think that 110" water lift and 200cfm should do it, not the job for a shopvac.
I have the Nikro dual head vacuum system that has 110" water lift and 230cfm and it will pick up water with my Steel Eagle 24" surface cleaner running 3000psi and 5.6gpm.
If you use nozzles to restrict your flow to about 3gpm, it would work better and you don't have to worry so much about a larger vacuum system.
You can get the Nikro and rig up a pump out system all for about $1000.00 but......you will need 3 outlets, each motor pulls 13 amps and the sump pump I put in mine pulls 9 amps, that is one problem with the system I have, finding 3 outlets not on the same breakers.
If you have a generator and some long 12gauge or thicker electric extension cords, you should be ok or if you can find separate breakers then you will be ok also.
Hope this helps.