<human>: Can you provide a brief overview of the text?

My 24 year old sister has been married for 2 years to a loving husband. A couple days ago she told me she was pregnant, but I'm the only one in the family who knows other than her husband.

My sister and brother-in-law live a pretty crappy house that they are slowly trying to renovate. They still don't have a fully functional bathroom. They only have one bedroom. My sister has a solid job, but my brother-in-law is still trying to figure himself out. 

They recently spent obnoxious amounts of money on two pure bred dogs, which they plan on breeding. My parents didn't think that getting two dogs, on top of their 3 cats, was a good idea, both financially and responsibility. 

My predicament is this: my sister plans on telling my parents about her pregnancy on Christmas morning, and she thinks they're going to have a fantastic response. She's getting me to film it. However, I don't think my parents are going to take it that well and it has potential to make Christmas miserable/ very tense. Should I spill the beans early to my parents so they can prepare? Should I tell my sister that I don't think they're going to respond well? Or should I just chill and catch an extremely awkward event on camera?
<bot>: My sister is pregnant and plans on telling my parents on Christmas. She thinks they'll be excited, but I don't. Should I warn them or do nothing?