My son and I worked on 2 sentences to describe his favorite part of each day. My daughter used a brainstorming web and picked a favorite part, and backed that up with 2-3 details. She also had to do an introduction and conclusion sentence.
The kids took them to school on Monday to share, and my son discovered that writing about his vacation was an assignment for the day- and he was already done ;)
I plan to make a summer journal for the kids out of composition notebooks, we will decorate the front cover and write in it throughout the summer to capture some of our favorite memories and to keep writing practice fresh for the next school year.