As a Consultant (hence the username), I often travel too much for my own good.... and as you will learn its all about managing expectation (i.e. client and your team).

On every engagement I have been running my workstream, I always start a holiday tracker and ask my members to fill them out and update the managers when something change. Its all about how you manage the expectation of your co-workers by giving them enough notice period.

If they ask you to change your holiday (i.e. due to client deliverables due the next day), it really depends on you as an individual. You can change your holiday (the firm and/or project will pay for changes) and or you go on holiday.