Elf house on a tree! That would be cute in the garden, especially in the tree over grown with ivy. How about some battery tea lights in the windows during outdoor parties. I hear the fairies/elves whispering "home school project" in my ear.
DIY lanterns: tuna can + glass globe + dowel or old broom handle + copper fitting + black spray paint 1 of 28 Outdoor Lighting DIYs To Brighten Up Your Summer For bigger projects use the chimney end caps at homedepot
Giant Tepee Garden - creative idea for repurposing branches and natural materials & provide an amazing play space for kids. They can watch climbing beans grow up as a natural shade cover, plant other edibles in the planter box around the edge.