A nearby stop is still another activity
Boti Falls and Umbrella Rock often appear in the same outing plan. Treat them as separate decisions. A group that wants a waterfall visit may not also want the walking involved in reaching another viewpoint.
Ask your guide to describe each route individually, including steps, uneven ground and places to rest. Don't accept a single duration for the whole excursion without knowing what it includes.
Make the second stop optional
Choose the main attraction before arriving. If Boti Falls is the priority, protect time for it and decide about the rock afterwards with the guide. If the rock is your main reason for travelling, arrange the day around that route instead.
This gives less confident walkers a way to enjoy the trip without feeling responsible for slowing everyone down. Agree on how the group will reconnect if activities differ.
Check conditions, not an old photograph
Waterfall appearance and walking conditions can change. Ask for a current update rather than expecting the scene in a promotional picture. Book transport with a clear waiting arrangement so a change of plan doesn't become a payment dispute.
Compare Boti Falls and Umbrella Rock in your plan as two stops, with separate time allowances. Remove the optional one if the day starts late.