Hi, Sara! Welcome to planDisney.
Managing different thrill levels and comfort zones is all part of the fun (and the challenge!) of travelling as a group. I love that you're already thinking ahead, Sara. This kind of planning pays off big time once you're in the parks.
For your situation, I'd avoid booking all four spots and then canceling two. That ends up wasting a perfectly good
Lightning Lane selection that the other two adults could use for something they do want to experience. Instead, go ahead and book the attraction just for the two who actually want to ride it. The other two can stay close—grab a Mickey-shaped snack,
browse the shops, find
Disney Photopass photographers and get some fun pictures, or even hop on a nearby low-wait attraction. You'll stay in the same general area without burning reservations you could be using more strategically.
Even though you want to split up as little as possible, these moments can actually be a great opportunity for people to purchase that special souvenir, re-ride a beloved attraction, or simply sit down to rest. No moment is wasted in a Disney park!
I trust you'll have a brilliant time, Sara. Thanks for choosing to be our Guest.
Mike