We are granparents traveling this summer to London with our two 9 year old grandsons. Am Marriott Gold and have Marriott points to use and have the choice of a Marriott Bexleyheath or Marriott Twickenham. Wondering if we are going to use all of our travel dollars on getting into London for the 5 days from either of these. I am not familiar with options for discounts on public transportation around London, so would be grateful for any help! Thank you!