I think See the tasty food is also correct as in talking to a group and pointing to the food
"Widzicie" states the fact that people you are talking to see the food. To convey the meaning you are talking about I would use another verb, maybe "Obejrzyjcie smaczne jedzenie" or "Popatrzcie na smaczne jedzenie" (="Look at the tasty food").
Oh a plural :) we have this in vernacular English, for example in southern US dialects they say "Y'all" - you all. In the scouse dialects of Liverpool, UK, they would says "yous".
I think what youre looking for is the imperative or a "command" tense. Im not sure about polish, but in any of languages I've studied, this tense has its own conjugation.
dz becomes sh in widzicie. dz becomes ds in jedzenie. Why do languages have to be so complicated ;)
dz does not become sh anywhere.
"dz" is generally like 'ds' in "woods", or it can be palatalized (dź / dzi), like in "widzicie" - and that cannot really be compared to any English sound, I think.
Because such verbs like "to see" (stative verbs) are really rarely used in Present Continuous, so we don't consider them correct answers unless there's something in the sentence to make them more probable.