If the Ewoks had been fighting the Imperials for long they would know that shields like those offered no protection, they are forest people and would need to set traps to hunt so more should be made of them using their environment as a weapon and shield.

Some of the traps we see in the film already only make sense if they know what sort of threat they are facing before the fight begins (and that's supposed to be a secret).

It would be good to see the Emperor's legion marching in to back up the troops the Rebels already know are there, only to have them picked off and worn down by traps set by the Ewoks who through stealth and observation have already detected their presence.

Setting up things like the big log traps in the few minutes Leia and Han are in the bunker without anyone noticing is beyond belief.

If they are to be kept the scale of the Imperial forces must be known to the Ewoks.