Have someone ride with him in the back if at all possible. Had to do this with my daughter and that was the only way she would stay awake.
I went through this with my daughter. My daughter was around 19 months and she is a kid who loooves sleep. The hospital where my daughter received care was 2 and 1/2 hours from home so we rented a hotel room and stayed within 10 minutes of the hospital. It was hard. I’m a single mom so I had no other help so I had my mom with me to help keep her awake. We took walks outside every hour or so. We did sooo many activities and games to keep her awake. - play doh, magnetic sand, coloring, you name it we did it. It was sooo rough. Be prepared for so many meltdowns. Exhaustion for both you and your son. If you can get help, like family, I highly suggest it. It’ll take more than one person and the meltdowns because of exhaustion are hard to take alone. I personally cried a lot because I felt so bad because all she wanted to do was sleep.
I don’t have much input other than I had an EEG when I was about 4 for my epilepsy and I remember my dad driving and mom was in the backseat with me to keep me awake with a portable DVD player with my favorite movies (cars = sleep lol and this was 20 years ago). I hope everything turns out well for your little one
Favorite show they get sucked into, Loud toys. If they like to sleep when it’s colder make it really warm or vise versa if the other way around. Rough house (wind them up). If they are like my son he is always hyper after a bath
I’ve it’s an option, someone ride in the back with him
take him to disney land
Have someone sit with him during the ride. We would sing songs or chat on the way. If it looked liked my little one was about to fall asleep, I would let her watch one of her shows on my phone. Just try to have a few things that could be entertaining. Watching shows was also very helpful at keeping her mind off of getting all the electrodes on and off her head for the EEG as well. Good luck!