Make two plans with a shared starting point

A riverside walk and a small gallery near the same station can use the same morning train. Check how the group gets to each place, current opening times, ticket requirements and the time needed to return. A nearby building that is fully booked is not a usable wet-weather option.

Set a decision time before the fork in the route

For example, meet at 10:00, check current conditions at 10:10 and choose the walk or gallery before the group leaves the station. If the gallery requires timed entry, move that decision earlier or hold an appropriate booking under terms you understand. Give everyone the final plan in one message.

Choose what survives if either option fails

Pick a time to decide which plan to use, then tell the whole group. If tickets are nonrefundable, review the actual terms before relying on a weather change. The indoor option is only useful when people can enter it at the time they need it.

If a storm makes the entire journey unsuitable, a different indoor venue in the same affected area may not solve the problem. The group can stay local or move the outing to another day. Keep the distinction clear between a little rain that changes the activity and conditions that change whether traveling is sensible.