Do my husband and I both have to have a travelcard to get the deals or can just one of us purchase one and the other just have an oyster?

while you'll probably get both answers you'll both need a paper travelcard for the 2for1 deals. If your plan is to use the Oyster for zipping around London just do what we did. Purchase two round trip tickets in and out of London like Clapham Junction for example that will cover the time period that you're there. For instance if you'll be in London June 1st through the 5th get two paper tickets for a trip into London for June 1st and departing on the 5th for someplace close like New SouthGate or Eltham....someplace close = cheap cheap. You won't be actually taking this short train ride but it does give you access to the 2for1 discounts

Thanks Tailsock!
We get into Heathrow and were going to catch the tube to Green park and then to Southwark (where we are staying).

Would I be covered for 2 for 1 vouchers if instead I trained from Heathrow to Paddington and got return tickets to Waterloo, using that one to arrive close enough to our accommodation and just not use the returns as we are catching the eurostar to Paris 5 days later.
Is this what you would suggest, I know nothing of London, any help would be great?
I just want the simplest/cheapest possible way to get the 2 for 1's

No tickets from LHR qualify for the 2for1 offers. A ticket to Paddington will only waste a LOT of money. A trip between Paddington and Waterloo would be by tube so that won't work either.

The simplest would be to take the tube or a car service to Southwark and then buy paper travel cards at London Bridge or Waterloo East - whichever is nearer where you are staying.

jenking,

janisj is right...a national rail station (not tube stop) is the way to go. we bought our paper tickets from Charing Cross if I remember right. also remember to print out the offers on the website ahead of time so you'll have them. What's interesting was of all the places we used the 2for1 coupons only one attraction actually asked to see our paper tickets and that was Tower of London.

How many days will you be in London? Sounds like 5 from your posts.

First, Tailsock's suggestion works if you're going to be there 4 days or less. Otherwise, the Oyster pay as you go cap will max out in less than a week - if you never travel the public transport in London during peak times, Oyster is a slight savings v. the travelcard for four days. If you travel at peak times, the Oyster cap (8.40/day) will exceed a seven-day travelcard cost (30.40) in four days. You're on the cusp and because you may not return your Oystercard for the 5 quid deposit, you would spend more on the Oyster PLUS a fare to Clapham Junction or East Croydon or similar.

Second, Tailsock's suggestion requires you to do exactly what you'd do if you just wanted the travelcard: go to a national rail station. So just buy the travelcard.

Bring passport size photos for everyone who will use a travelcard.

Do this right and use the two-fers. The savings on the Tower alone ($32 per person entry fee) will make all the trouble worthwhile.

i'm curious about the 2 4 1 offers. it applies to the tower obviously. are there other things that are useful?

Yes, many. St Paul's, Hampton Court Palace, Cabinet War rooms, etc etc . . .

www.daysoutguide.co.uk lists all the available deals