Hi Lara,
Welcome to the Disney Parks Moms Panel! I am glad to see that your planning process includes considering the ride drops. When we took our girls to the Walt Disney World Resort for the first time, we went through a similar planning process. We discovered that they loved everything, small and big drops!
My husband hates roller coasters but even he enjoys
Seven Dwarfs Mine Train (where we all sing Heigh-Ho with the Seven Dwarfs) and
Big Thunder Mountain Railroad. Both are listed as having small drops. They do have hills, however, so I would suggest that you also consider whether or not the person dislikes the roller coaster climbing the hill, the drops or some combination of both. Expedition Everest - Legend of the Forbidden Mountain, Space Mountain, Rock "n" Roller Coaster Starring Aerosmith and Twilight Zone Tower of Terror are all probably rides you want to avoid.
Other rides like
Frozen Ever After and
Pirates of the Caribbean, also have small drops. They are both slow moving boat rides so the drops are not overly dramatic (in my opinion). They are simply downhill. Before our first visit, we searched ride videos on YouTube so we could get an idea of which rides might be too scary for our girls. I just checked and saw videos of Frozen Ever After and Pirates of the Caribbean currently on YouTube.
Lara, we find the vast majority of rides to be perfectly suitable for the whole family but you know your group best!
Magic, memories and Minnie Mouse hugs,
Donyell