I'd look at the other outdoor activities thread. Think through many of those activities from an "I feel, i hear, I touch, I smell" perspective and you have good sensory activities. I usually leave out "I taste" unless I know the class well
Conversely, if you had specific senses you want to focus on, such as touch for that one student who touches everything, you can look at your outdoor spaces. What textures are there? Can you categorize the textures? Dothe textures change? Can you create class names for the textures? Later, can you discover texture words and create a class dictionary with examples? How would you draw texture? Can you create texture scavenger hunts?
Just some ideas. I am sure you will come up with and share many more!