The cheapest way in. The Elizabeth line and DLR to London City Airport is 12 minutes quicker for £9.60 more, which is not worth it at this party size.
Piccadilly, Jubilee and DLR to London City Airport
PiccadillyJubileeDLR · Transport for LondonPickup, hours & luggage
Boards at. Heathrow Terminals 2 & 3 Underground station, or Terminal 4 or 5; changing at Green Park and Canning Town
One fare for all three trains: £5.90 by contactless or Oyster at any hour, tapping in at the Underground station and out at London City. A paper single is £7.00.
Luggage. No stated limit, but these are Tube trains and the Piccadilly line has no racks.
Hours. From Terminals 2 and 3 on weekdays; the last DLR to the airport leaves Canning Town just after midnight. On Sundays the Underground starts later.