FreePBX 2.8.X (and perhaps earlier versions, I don’t remember when it came out) allows you to ‘nest’ Time Groups. Create a Time Group called Holidays. Enter your first Holiday criteria, click Submit and a new set of fields appears. Enter your next Holiday criteria, click Submit and so on. (I have six Holidays in one Time Group and I’m sure you can enter more.) Then, create your Time Condition called Holidays and use this new Time Group. The ‘Destination if time does not match’ should then be your ‘Regular Time Condition’. The Inbound Route should point first to the Holiday Time Condition before any others.
The only challenge left is to remember to change the Holiday Time Group next year for Holidays that have date changes! i.e. Christmas is always the 25th, but Thanksgiving moves around.