Re: working on Christmas?
I presume your parents are
adults. So, they ought to understand this dilemma you have, as adults. Not everyone has a 9-5 job. Remind them how lucky they are you are not out of country---such as military people, or contractors overseas, at their holiday time. Imagine how tough it is for people whose loved ones are in the Middle East or someplace else far away this time of year!
Suggest alternate ways to enjoy your time together---maybe having "Christmas" on an alternate day or something. There are other ways to celebrate a meaningful season like Christmas than the traditional ways ---you may have to be creative. It's not about dinner, gifts, trees, etc anyhow. Any adult knows that.
Now, If their problem is your asking them to keep your kids for you, you may want to ask someone else, I don't know. They should feel LUCKY to have their grandkids around this time of year. Again, many other grandparents are not that lucky.
I think some people just need a reality check as to how fortunate we are......
At least you are explaining this to grown people---it's harder usually, for children to understand why Mommy or Daddy are not around (being military, it's been our way of life for so long, but it's never easy). If my kids can understand this concept, surely, your parents should be able to! Good luck.