Family options for Eurostar

Looking for the best way for a family of 6 to get under the English Channel and have a day trip to Paris. Is there a "family style" ticket for Eurostar from London to Paris? We discovered that a family of 6 can travel a lot more cheaply on the Frecciarossa trains with a family ticket than if we bought 6 individual tickets. Hoping there are similar options on Eurostar. Mom, dad, 4 kids aged 15-10

Any other travel tips are appreciated: Staying near Buckingham Palace week after Easter 2018