I think the trouble with this approach is that our robitcs are not nearly robust enough for these sorts of tasks. I've had two DVD recorders break down in a year in an environment no more hostile than my living room. Any sort of breakdown jeapordizes everything: a bolt breaks? No tunnel. A wheel gets stuck in a sand dune? No more water processing.
A human being, however, can repair the inevitable breakdowns, mis-steps and unforseen events -- even if they are catastrophic, as happened with Apollo 13.
The robots have to be designed with several things in mind. First is "task simplicity", limiting the robots as to what they can do--which goes against the grain at NASA.
Second is to seal components instead of lubricating them. To keep to a bare minimum parts exposed to extremes of temperature and dust.
Third will most likely be a repair robot for parts that need predictable replacement, like rock drilling bits. This robot stays on the grounded spaceship most of the time, just exiting periodically to work then return. Since this would be the most complicated robot, it would be most sensitive.
The entire robotic team can be "trained" on Earth ahead of time, performing its tasks in all sorts of situations, so that when it arrives on Mars, it can be programmed for the most likely scenario of operations.
Since the US is planning unmanned rockets with a 100 ton lift capability in the near future, the logical process would be:
1) Construct a large "shuttle" rocketship in space, then haul up enough fuel for it to make a round trip to Mars.
2) Send up modular pieces of the Mars lander with the robots and nuclear reactor inside. In orbit, they are fixed together, then attached to the shuttle rocketship for the transit. They only need enough fuel to land.
3) Transit to Mars ends in Martian orbit, where the shuttle and the lander separate. The shuttle stays in orbit for a while as a high-power transponder with Earth. The lander lands next to a large vertical rock outcropping selected as suitable for a horizontal tunnel network.
4) Initially the nuclear reactor, the tunneling robot and the tailings robot/scoop bulldozer approach the rock face. The tunneling robot begins to grind away at the rock surface, catching and passing the tailings underneath it to the tailing robot behind it. When it is full, it backs away and dumps the tailing away from the entrance. When the tunneling or tailing robot need energy, the nuclear reactor approaches them with a high current male connector and recharges them.
5) At intervals, the tunneling robot drills verticle holes in the rock ceiling and inserts low-weight ceramic reinforcing rods to add extra stability to the rock. Periodically, the tunneling robot backs out of the tunnel so that its bits can be replaced by the repair robot.
6) After a significant amount of tunnel and a vertical cistern has been mined, a low pressure micro sealing agent is sprayed on the inside of the tunnel walls and ceiling. Reinforcing members are cannibalized from the lander, as are the pressure doors, and even "flooring" material.
7) With the creation of a first "habitat", these robots can move a suitable distance away and begin the process again on a different rock face. Other robots can then be activated on missions such as scouting for and mining water.