[Al Skierkiewicz]

Adam,
Since the battery is not likely to produce the full 27 amps if all motors stall, it is unlikely that any one motor will draw more than 7 amps. If you keep the wiring short and a match is only a few minutes (using the chart linked above) you could use #22 for each of the motors without damage. I am guessing that your 3lb robot is not very big so the weight difference between a #22 and a #18 is not going to significantly change your weight budget. The #18 will supply more power to the motor and would be the better overall choice. As always, the electrical design is important. Keep the leads short and distribution to the motors should occur as close to the power input as possible. You do not specify that a fuse(s) are required but at least a main fuse should be considered to protect the battery.
You also did not specify if the batteries are in series or parallel so I am assuming they are in series. As such the maximum current from the pack is still only the single battery current spec, 30C x 1 amp=30 amps. This is in keeping with the #14 wire suppplied. Using the wire table again, notice that the specification is the chassis wiring column. #14 is good for 32 amps in that situation. All wire/current is rated by temperature rise in the wire and this table only lists open fram or chassis wiring. Other tables will list current or "ampacity" based on open or closed applications. The table lists the maximum amps for power based on the 700 CM/amp (circular mil or effective cross section of copper wire) rule. In general this computation is designed to give at least 80% of the input voltage at the load for a given length. None of these applies in a small wiring job. Even a foot of the #22 at 9 amps would only drop 0.14 volts. You may find some wire with a lightweight teflon insulation that could significantly reduce your weight allowing a #16 to be used at less weight (but more cost) than a PVC insulated #18.
If your battery packs will be wired in parallel (something I never think is a good idea without diode protection) than the #18 is the only choice. BTW #20 wire is difficult to find that is why I did not consider it in this discussion.
If our assumptions are incorrect or there are other rules to consider, just let us know.