nice quite beach area end of December family of 4
 

where to go end of Dec for 2 weeks, 2 kids 11 and 13, nice area, good food.
any tips thank you.

The Christmas holidays are an extremely busy (and more expensive) time at the beach resort cities in Mexico, you'll want to make reservations soon.

Depending where you are flying from you could look at Mayan Riviera (Cancun, Playa del Carmen, Akumal) or Nuevo Vallarta (the coastline to the north of Puerto Vallarta)? Zihuatenejo/Ixtapa further down the Pacific coast.

Barra de Potosi outside Zihuatanejo would be ideal.

hotellaspalapas.com

If you are considering the Caribbean side, you have lots of options. For quiet beach, you could choose Akumal or Tulum. They both have very beautiful beaches and good food options. They are quite different from each other. Akumal offers calm water, great snorkeling. Tulum offers vast expanses of uncrowded beach, sometimes heavy surf. Go to locogringo.com for tons of info, pictures, maps, hotels, etc.

You should also look into condo rentals in the areas mentioned. That works out well with kids, especially being able to have snacks and drinks available, and even eat a meal or 2 at the condo (great take-out bbq chicken places in PDC). What's also nice about PDC, is that there is a wealth of restaurants (and large grocery stores) within walking distance (as long as condo is actually in PDC), although the beaches may not be as peaceful (could be crowded) as they are in Akumal and Tulum.

Bear in mind that even condo rentals cost about double the regular rate for Christmas week.

I'd split a two week stay between Cancun and somewhere quieter like Tulum or Akumal.
The first week should be cheaper as it's not a 'holiday' week.

We're going to Cancun and Akumal for Christmas this year and we'll use hotel points for part of the stay to avoid the inflated holiday prices.

There are few early discounts (mostly if you prepay) but if you are prepared to wait you might get a late deal so book something now that you can cancel if cost is an issue.