It will be interesting to see how you like the Underground. We actually rode it to Holborn from Heathrow airport on the Picadilly Line. It can be crowded but it is really economical. 6 pounds versus 65 pounds for a cab. The Oyster card is really handy. We also rode the underground out to the RAF museum in Colindale. ( A short walk from the station to the museum). Just be sure to use the Underground during the off hours. We left Holborn at 8:30 one morning - what a zoo.
Let me know what your husband thinks of the RAF museum. I liked the planes a lot but they need more room.
I have big time trip envy. Have fun.
We did pre-nights at the Chancery Court this past June (prior to the Disney Magic trip to the Baltic)--we stayed there at xmas 2008 for the ABD K&L trip and really liked the location. This June I convinved my DW to take the tube from Heathrow to the Holborn station--she was leery, but in the end agreed it was easy, economical and fun. Easy one block walk from the Holborn station to the hotel--there is one set of stairs (not too steep or deep) that you have to carry your bags down at the Heathrow station, but other than that it was easy. There are 22 stops from the airport to Holborn, so plan on an hour or more on the tube--but it is confortable, and room for bags.