Should we book TUI excursions in advance or wait until we get there?

[thirdistheonewiththehairychest]

Would it be more expensive to wait until we get there (Mexico)?

Might there be more options that are advertised?

What would happen if we pre-booked something, only to find out when we get there that it's not really suitable for our 5yo? (specifically thinking of a 'snorkelling with turtles' thing...)

Never done a package holiday before so not really sure how it all works. Thanks in advance for any helpful advice!

We haven’t done package holidays but if we want something organised we use Viator - good range of activities across the world
https://www.viator.com/Mexico/d76-ttd

We always wait until we are there. You can often get much cheaper excursions outside the resort.

I always book them with Tui even if they're a bit more expensive. You know they're going to happen and that they're going to be well organised and safe.