Yes, Klikaklu is great for a car rally. Distance is not a problem. The last car rally I did worked really well. I put two or three clues in each drivable area. People really got competitive, with one team rearranging/hiding the subject of a clue (a bemused bystander helped other teams), and another team hid the car keys of a team that for some reason left theirs in their car (with the engine running!). The final destination was a yogurt shop, where teams straggled in as they finished. It was a blast.
The big issue you will want to consider is how to break up the groups so they don’t all do the same thing at the same time. You can do a scavenger style hunt (where the clues are all revealed, and your players find them in random order) or a treasure style hunt (where the clues are revealed in order).
If you do a scavenger style hunt, you will want to inform your players somehow not to do them in order, maybe tell each one to start with a different one.
If you do a treasure hunt, you will want to stagger the start clues for each group. When you create the staggering, if you have more than a single clue in an area they drive to, make sure only the first clue is eligible for as a start clue (you can adjust these after tapping “Stagger Start Clues” from the Hunt Details screen). Otherwise, you’ll have some teams having to return to the same location a second time, which won’t feel fair.