Do gorgeous fairy garden--Stepping stones with children's hands or foot prints is a nice way of allowing your kids to feel involved and leave their own mark on your garden as well as providing a small snapshot in time for you to remember and enjoy.
15 Easy DIY Projects to Make Your Backyard Awesome
Rust-Oleum Glow in the Dark Brush-on Paint Line a pathway with rocks painted in glow in the dark paint. During the day they "charge" in the sun and in the evening they reflect the stored light. Rust-Oleum Glow in the Dark Brush-on Paint.
"Customize Your Outdoor Spaces – 33 DIY Fire Pit Ideas, plenty of good ideas to choose from (cheap too)" We'd like a firepit but most of our back "yard" is taken up with a 1200 sf deck on two levels, overhanging a gully.