Chantel, I began a response about 10 minutes ago, had to leave my screen briefly, and my time must have expired. I hope it simply disappeared, and was not sent to you in its beginning stages.
Firstly your approach, "Stop! Wait! Come Here!" is a form of "rehearsal", with your young child, and sometimes with older children. Establishing special, repetitive,
"rehearsal" words in a warm, supportive tone, and repeating them in various situations, are likely to have a memorable impact on your walks outside. You might begin with special stuffed animals, pretending that you are about to go out.
Singing your "rehearsals" impacts children's enthusiasm and their memories. "Let's play go outside, with bear, doggie and turtle" for example. When we need them, we say (in a warm, loving supportive voice,) "Now, we stop! What do we do when we stop." Demonstrate the motions that reflect "stopping". Do the same with "Wait" Make it fun, memorable and repeatable. Then when you are ready to go out for your real walk, remind your son, before opening the door, "What do we mean when we say, Stop! (He rehearses it! ...... Wait! Rehearsal ... Come Here!"? Again rehearsal! This is done with smiles, a certain playfulness, words, many repetitions, and affirmation, as in "I knew you could do this!" Struggles around walks will become fun. Repetition and affirmation will turn this into a game, played inside and out, and then into the real thing. When this montra becomes 2nd nature, walks may turn into nature walks, seeing rocks, leaves, sticks, moving insects. The world becomes his laboratory of learning! Good luck!
About me: I am an educator why has been working with children and adults for many years. I have 7 grand children, ages 3 - 19, and have successfully modeled "rehearsals" in many contexts. I wish you success and am confident that you and your child will experience joy in your outings.
Best Wishes, "Nanasource"