I agree - although ‘on’ has multiple uses in modern French (see link) it does appear here as if he switches from me/my holidays to ‘we’ without explanation of ‘who else’. 

The use of ‘on’ instead of nous is colloquial and definitely current, and even if he started with a ‘nous’ at the changeover, it would still be uncertain who the ‘extras’ were. It seems to me almost as if the script was edited or partly re-recorded at some time and the updates weren’t comprehensive.

Could do with an extra line in the dictation, or a hint/explanatory note at the point that he switches to ‘on’.

https://www.frenchtoday.com/blog/french-grammar/understanding-french-on-subject-pronoun/#on-instead-of-the-passive-voice 

PS I don’t disagree with Tom’s comment at all. In a conversation, clarification could/would likely be sought when he switched subjects.

But neither does he necessarily imply that he is going alone. He simply begins the story with some preliminary references to personal plans and preferences, before naturally broadening the picture to reveal that he will be part of a group.

Yes, of course. I was looking for a more subtle and deeper interpretation.  Since "on" and "nous" can both be used, why does he choose "on"?  What leads him to switch to "on" at the point he does?  If I had written this paragraph in English, I would have provided some explanation of who "on" is.  In part, I am saying that without an explanation, this paragraph is not well written.  Unless, there is some clear clue....

Maarten,  thanks.  That's a good analysis.