RE: THE BANK
There is only the one entrance, which is currently a gaping hole(aprox 10' tall 15' wide) in the front of the bank.
Considering it's slowing several super-villains, busting in THROUGH the vault (Which takes up the entire back) probably won't work..
THOUGH, if you wish to try vapourizing the back wall of the vault, destroying whatever happens to be in that section, and giving the villans an escape route, go ahead.

Some options would be: going in through the side (Easier to blow out the wall), or the front where the 'door' was, while your comrades distract Sabretooth/Blob, Or coming through the ceiling (though not the vault part probably).
ALSO, anybody wishing to shoot through the open 'front door' can hit either Blob or Sabretooth at a -4 for cover. The vault cannot be seen from outside.
The point of the excercise is to see what you guys do left to your own devices. Don't be scared that it's not going to go off with military precision - You're kids.