How is the weather in rome/venice/tuscany for last week of may and 1st week of june? If you are not visiting a church, can you wear daisy duke shorts, mini dresses, tank/crop tops etc in those places or is it a big no no?
It is never appropriate to wear Daisy Duke shorts, etc. in any of the churches in Italy - and many will block you from entering. I would also suggest that you refrain from anything too revealing while touring Italy, it could draw unwanted attention from those who don't know how to behave, and this would be unfortunate while you are on holiday.
If you feel the need to dress like this, then it would be a good idea to carry a large, light weight scarf that you can use to cover up while entering into the churches, in many cases this is acceptable.
Late May and early June might actually not be that hot yet. It has been a cold winter so far and predictions for this year are that it will be a mild spring and summer. So late May might actually still be cold.
In the churches, all would be a no-no. You would need a large lightweight scarf you can use to cover up bare shoulders and another to use as a wraparound skirt to cover legs at least to your knees so that you can even enter them, otherwise they will turn you away at the door.
Tanks and shorts are fine for walking around, but not daisy duke style.
Shorter shorts would most likely attract undue attention from those that don't know how to behave themselves so just a little longer would be better. Consider wearing cropped shorts/tights under mini dresses for the same reason.