I have tried several strategies for this mission, but I can't seem to get enough command points to mount a serious offensive against the Ion Cannon emplacement...can nayone help me get started? what units should I start with?

I don't know If the way I did it is the best but it worked for me.

I attack the base just above the ion cannon implacement first, nice and slow with the AT-AT clearing the way with its chin gun and catuping a secod AT-AT with some more infilltrators. Once the supporting troops where knocked out not to mention the extra command points taking out the second lower base wasn't too tricky then slow and steady march for the AT-Ats taking out the Artillery and then take the ion cannon blow up the star destroyer and away!!

Good Luck