Looking for some advice on calendars / scheduling around holidays

Hello All,

So, we've got two christmas calendars:

Ours - late December to early Jan

Site - Mid December to slightly later Jan

My project's standard calendar that i try to use for all activities has our public holidays

We have some activities that our to be done on site that need to have a site calendar assigned to them.

Previously, our on site activities were falling in November so it wasn't an issue.  But now they fall into late December when WE are working, but SITE is not.

What i'd like to be able to say is 

"If any of 'these' activities fall into this timeframe, then move them forwards" - i dont want it applied to all activities.

How would you schedule this?

At the moment, i think the only option is to give those site activities a specific calendar, and if they continue to drift right, change the calendar back again.   But this is problematic for scenario planning

Any thoughts?