I've used magic play dough on the first day of school for the last two years and it works wonders! It's a great first activity that all students are capable of completing and it will give you a chance to get everything settled. It can also be used afterwards as a great assessment tool. For the younger grades, you can use it for things like creating letters or numbers. Older students can build things like what they want to be when they grow up, what they like about school, or their favorite book character. This is already very popular online, I just created my own poem.