Main Idea and Details

Some of my 3rd and 4th graders are having a difficult time with identifying Main Idea.  Some just are not getting past the idea that not every paragraph or passage will have one sentence that will state the main idea.  Others are just looking at the title of the piece and considering that the main idea, thus missing a lot of detail.  So I really wanted to do an activity that pulls them away from text but still addresses the concept of main idea.
I decided to create bags full of items that go together.  The students have to think about how the items relate to one another and ultimately what the main idea would be of all of the items together, as I slowly pull them out one at a time. One item is the key item that really ties everything together, the detail to best support the main idea. It worked really well!  The kids loved it! 
For the first bag I used a medium-sized tote that I used to use as a purse and we started by discussing what the bag could be used for and what could be inside (right away they guessed items that would belong in a purse).  Inside I had a snack-sized bag of mini-cookies, a napkin, an orange, a drink, a spoon, and then a container of soup. 
When the first few items were pulled out, we talked about how they were food items and would probably be eaten as a snack.  When the final item, the soup, was revealed, then they knew that all of the items together meant, "Eating lunch."
The soup was the key item, the detail to best support the main idea.  I have also put some additional bags together (baking items, swimming items, etc...) all with one key item to tie it all together.
I uploaded the plans and printables for the first bag below.
I would love to hear some of your suggestions for teaching Main Idea!