To talk about events in the future that we've already thought about and intend to do:
Example: We're going to hire a bus. (Intending to go, but arrangements aren't finalized)
To make predictions based on present evidence:
Example: We're certainly going to have a varied trip. (Based on plans and knowledge)
Choosing Between "Going to" and "Will" for Predictions:
In many cases, the distinction between the two isn't significant, and either can be used to express a future prediction. The choice between the two often depends on the speaker's preference, the context, or the specific nuances they want to convey.