Re: The Queen's Platinum Jubilee Celebrations June 2-4. What do we need to know about the event? Disruptions to tube schedules? More crowds, harder to find accommodations? I'm not familiar with this so not sure what to expect.
Nobody else is familiar with a Platinum Jubilee. This is the first one, so its new to us too. But based on previous Jubilees of Her Majesty Queen Elizabeth II, unless you are near a particular event in central London you might be hard pressed to know that there is one on. You may find street parties in residential neighbourhoods and it might be well to think about crowds around the Mall, Trafalgar Square, Buckingham Palace, Whitehall, etc. You may well find more difficulty getting the rooms you want at the price you want to pay in Central London over the weekend. But we are used to big events here and if you aren't where the action is you will pretty much see life as normal. Well, as normal as life can be during a pandemic. Who knows what it will be like in May and June? My wife and I are still in isolation after 2 years.
Are we better off with backpack type luggage, or are roller bags good? Thinking about sidewalk/street surfaces and what might be the best.
London, and the rest of England, has very little cobblestone. Expect pavements (sidewalks) of paving stones, concrete, or asphalt. Quite smooth except around tree roots in some places if the pavement has lifted. Most but not all corners will have pavement cuts for wheelchairs - much less in the rural districts. Roller bags should be not much trouble - go with what you prefer.
Our flight leaves out on 4 June from LHR. Should we plan a hotel closer to LHR the night before, especially considering the jubilee celebrations? The flight leaves at 1315, and we need to be at the airport by 1100.
For a flight to the US? You've been here before so have your own experience, but 2 hours is brave. Even before the pandemic 3 hours was the normal for transatlantic. 2 should be ok for domestic and Europe. The Jubilee is unlikely to make much difference at Heathrow. For such a late flight I wouldn't move hotels for one night. Tube takes an hour. You can even have a leisurely breakfast.