Dear Ruth and Sandra,
I think it's a good idea to meet up at a lounge before departure as it gives you a relaxed, quiet location to meet and get to know each other. If you're interested in booking a lounge you can use the Riviera extras webpage (link below) to do it. I would recommend booking sooner, rather than later, as lounges can become unavailable for certain time slots (the lounge companies limit the number of entries to maintain their cachet).
Also (and this is more important) be aware that there are two lounges available at Heathrow terminal 3 (No 1 Lounge and Club Aspire), so that if you want to meet up ensure that you book the same lounge!
Erik.
https://www.holidayextras.co.uk/riviera ... unges.html