Hi. We're a family of 4 (kids 11 and 14) who have hotel reservations for 7/6-7/9 in Paris and 7/10-13 in London. It's going to cost me an arm and a leg to add a night at either hotel for the 9th. So, I was thinking, as long as I have to switch hotels, why not switch countries and do a short stopover in Brussels or Lille. Any suggestions on which I should choose? (I have to admit that just judging from hotel prices, Brussels looks much more affordable.)