Christmas in England

For Oxford look at www.dailyinfo.co.uk, and for London try Time Out or the Londonist.

If you don't already know, the big warning is that there is almost no public transport in London on Christmas Day, while on Boxing Day there are local bus and tube, and long-distance National Express bus services, but almost no long-distance rail. If your accomodation on Christmas Day isn't self-catering, I would start looking for local places to eat a while in advance, as few restaurants open on Christmas Day and those who do tend to book up early.

Philip beat me to it but just to reinforce it. Basically England is shut down for Christmas Day and Boxing (Boxer?) Day - can never remember. I would like to rent an apartment somewhere for that time period.

A boxer is a person who bashes another in the nose or a breed of dog from Boston.

Boxing is the giving of a gift in a box, or envelope, to a servant or service provider on the day after Christmas.

It is Boxing Day.

Exactly which area are you seeking advice for, Oxford or Greenwich?

Travel plans MUST keep in mind how England comes to a stand still on Christmas day. Be prepared for that.
In other words either have food to cook or make reservations for dinner out. Research to see who is serving a meal on that day. Local pubs and hotel restaurants would be your best choices to research.

As far as special exhibitions or concerts at Heathrow purchase an issue of Timeout Magazine. Will list everything concert, etc. From experience I know the Turner Prize exhibition will be on at Tate Britain. There are always excellent exhibitions at the Photographer's Gallery near Oxford Street.

As far as Oxford I would peruse this website; http://www.inoxford.com

As far as pubs http://www.fancyapint.com or http://www.beerintheevening.com should help you locate something near where your accommodations are.

My favorite London pub for it's Art Deco beauty is The Blackfrair http://www.nicholsonspubs.co.uk/theblackfriarblackfriarslondon/findus/
Right across the street from the Blackfrairs Underground Station

Dress in layers, pack light and remember it's Winter. Sun will start setting around 4pm.

Definitely look into making a reservation at one of the pubs if they are open on Christmas (and make reservations soon). Maybe the Gypsy Moth which is near the Cutty Sark, Trafalgar Tavern or the Yacht?
Then, since everything is closed on Christmas, just walk around Greenwich since public transport is closed. And take a walk through Greenwich Park, assuming the gates are open, great views if you wander up the hillside, if its a clear day.

And, when public transport is open, take the ferry at least once from Greenwich into London, its nice.
http://www.thamesclippers.com/find-your-pier

Do not miss Evensong at Westminster Abbey on Christmas Eve. Check their webpage for this year's schedule. It is first come first served. It was a highlight of our trip there 10 years ago!

Your family might enjoy the Hyde Park Winter Wonderland with its Christmas market, rides, food vendors, etc. it is particularly pretty at night but now in December it gets dark very early so your little ones would not have to be out too late.