Thanks, Marco. I was unable to find any definite information on the paper Travelcards.
Diana, since you will be in London for 11 days ( lucky you) there is another option. Regular (paper) train tickets into and out of London will qualify for the 2-4-1 offers for the entire period between the journeys. So, if you are planning on some short excursions out of London by train (Bletchley Park, Windsor, Richmond/Kew, etc.) you can put one near the beginning of your stay, and the other at the end. Use the return ticket (into London) from your first trip and the outbound ticket for your later trip as your tickets to show for proof of travel. You must hold onto the first ticket—don’t put it in the regular turnstile when you exit the station, go through the manned gate and tell the agent you need to keep the ticket). And buy your tickets for the later trip early so you can show those as well.
This may sound complicated but it does work.
For your trip from Heathrow into London Paddington, it would be simpler and less expensive to buy online tickets for the Heathrow Express 90+days ahead of your trip ( so buy them in May). Those tickets are £5.50 each, instead the £12.50 fare for the Elizabeth line. It is also faster— 15-20 minutes on the HEx, depending on your start terminal,mversus 40 minutes for the Elizabeth line.
Note that the Heathrow Express tickets do not qualify as “travel into London” for the 2-4-1 offers.