Dec-Jan High Season Travel - hidden gems?

Hello everyone,

we cannot help it, we "only" get travel time this year from Dec 8 to Jan 5 - which is pretty much high season period in Panama (mid dec- mid jan) - unfortunately. Reading here and there, I am bit shocked about prices and not sure what to expect in terms of great places being "booked out" and hordes of package tourists around...

Anyone to give advice on ...
... great, remote places without the (xmas tourist) masses? ie affordable beach locations, great diving/surfing around, top spot for spending xmas days on the beach, "hidden gems"
... places to absolutey avoid? I am guessing Bocas del Toro (full of US tourists?)
... skipping the idea of "pack and just go"? Do we need to pre-book pretty much everything? flights to San Blas?
... anything else important we need to know at this time of the year?
... combining other countries / areas into our travels?

We are both mid-30s, well traveled, experienced backpacker couple - but no longer relying on a shoestring budget. Mixing accomodation from low-key beach bungalow to (occassionally) a luxurious eco lodge type of place. We like nature, diving, surfing, trekking and ... less partying all night.

Last year we travelled in Nicaragua in Nov/Dec- what prices to expect in Panama in comparison? (in high season)

Itinerary:
HOME-Miami 2 days-Panama City-~3 weeks Panama-1 week parque nacional corcovado (Costa Rica)-San Jose (1 day)-Miami-HOME (Germany)

Muchas gracias a todos!
Ingo (& Dorothy)