HDR shooting best alternative?

I use a Canon EOS 450D. This allows either mirror lock up OR bracketed exposures. I'd like both!
At 3 frames a second in exposure beacketing mode, will the mirror be bbouncing all over the place? Or does it stay up for the three exposures? (I think not).
In mirror lock up mode the time between exposures means the tide has probably come in and gone out again, or the clouds have disappeared, or the leaves have changed colo(u)r with the season change. Maybe not that slow, but you see what I mean.
Anyone ideas on which is the better solution?
Chris Bishop