texas and xyz: i think the PAYG Oysters at LHR for 3 adults and 1 day travelcard as needed would be best for us.
here's more info about the 3 of us: we are all adults as in waaaaay over 21 yrs old and will day trip out of london 2 out of the 7 days we are there ( but we still need to get to PAD from our hotel to pick up car or take the train-still debating on this for the daytrip to Bath) we will be staying at the Hilton in Park Lane (closest tube stop is Hyde Park Corner and closest rail office is at Victoria station, acc to the tube map)

texas, thanks for the clarification about use of the PAYG. i was under the impression that all 3 of us can use the loaded credit in the card, as needed. if i understood you correctly, PAYG will work with just 1 person, so each of us has to have our own PAYG oyster AND a 1 day travelcard (for the days we need the 241 offer.) i think this approach eliminates duplication of "paid" days.

another question i have is: if we have any unused credit on the payg oyster, we can get this back as well as the oyster card deposit, as we leave UK from LHR. did i understand this correctly? thanks.

The odd person out will not need to buy a 1 day card--he/she will just need a bit more on PAYG Oyster than the other 2.

Yes, we got our unused credit back one time (and the other time just kept the Oysters and when I was back a year later, I used those cards--they don't "run out.") You will have to allow time to do this at LHR. Assuming you are flying out of there.

A couple things about said credit: It will be easier to process if you don't mix how you got the cash loaded onto the Oyster and don't have TOO much left. We had topped up our cards using both cash and credit AND we had over 10 pounds left on one--both of those could have prevented us from getting refund, but we had a ticket agent who bent the rules. I won't assume that could happen again. And I don't know what the "official" limit to refund. I think I've read recently that if it is over some amount, (?) they might not give you cash but would send a check. Or something. Anyway, just check what your balances are as you go along and add reasonably small increments as needed.

Glad to have/hope I helped.

texas, great point about the odd person not needing a 1 day travel card. person #3 can be on payg from day 1, upon arrival at LHR. and yes, we are flying out of LHR to return to the US.