I'm offering a free download of my TeachersPayTeachers activity that involves a first experience with calculating area.
The big IDEA behind this activity is that area is the space inside a shape. You use one inch color tiles to measure that area. If you don't have color tiles yourself, borrow them from the 3rd or 4th Grade teachers in your building. They will be very happy with you for giving students the experience that area IS THE SPACE INSIDE A SHAPE. Students mix up area and perimeter all the time, and they need to know the difference.
I'll leave the activity at "Free" for the next two weeks to give you time to download it. Please take the time to rate this activity. I'll appreciate it :) I haven't had the TPT account for long, so I will be adding to my collection.