Travelcard + Oyster...can a local double check my plan?

Peggy , you're quite close - Firstly , skip the visitors card and buy the cards at Heathrow . Pay cash for both cards ( 7 day travelcard and paygo , it will be very easy to get the refund when you leave . The computer will automatically deduct the difference between boundary zone two and heathrow from the paygo amount . As for the trip to Windsor - whether you go from Paddington or Waterloo to Windsor depends on where you start from . We were staying quite near Waterloo Station ,so it made no sense to go to Paddington to get the train to Windsor Central . We bought tickets at Waterloo from boundary two to Windsor and Eton Riverside . It was a short walk to the castle . If you are closer to Paddington , then go from there . Keep in mind that both the paygo and the seven day travel card are loaded onto the oyster . You will be capped by the seven day card to the zone two boundary ,and anything past that will be deducted from the paygo , it is actually quite simple and works like a charm . Don't be concerned about articulating your wishes when buying the cards , the personnel at the counters will perfectly understand what you have elucidated here , after all , this is England , not America ;-)

As there are 2 of you, are you not interested in the 2 for 1 offers available with a paper travelcard issued by National Rail?

http://www.tripadvisor.co.uk/Travel-g186338-c195600/London:United-Kingdom:2.4.1.Travelcards.Step.By.Step.html

http://www.tripadvisor.co.uk/Travel-g186338-c133479/London:United-Kingdom:Paper.And.Oyster.Travelcards.2.4.1.Offers.html

http://www.daysoutguide.co.uk/

Yup. This is it. So easy! I believe what I asked for was a 7 day Zone 1 and 2 and "enough extra to get me there and back." It was all on one physical card. When I flew home, I returned the card and spent the returned cash balance (including deposit) on a meal and munchies for the flight. It was super, super smooth and convenient transaction both times.

In regards to catching a train at Paddington to Windsor, check the timetables and prices. Something I did not do! The early morning fares are more expensive. The ticket agent was helpful enough to point out that if I purchased tickets for the next, next train, the fare would be less. So I did that and then didn't have to hustle for the "next" train which was leaving shortly. I bought a coffee, relaxed and people watched! So fun. Still arrived in Windsor before the crush of day-tripping tourist buses.

One additional comment ; The remarks about the two for one pricing are well worth considering , and the letter of the law , as it were , is that you need the paper travelcard . That is certainly the safest way to do it . However , from a purely anecdotal perspective , we had the cards loaded on the Oyster , picked up the brochure and vouchers , and used them anyway , no one batted an eye . Again , this was only our particular experience , used them at Cutty Sark , Hampton Court .

The only valid Oyster card for the 2 for 1 offer is an annual one with a gold record card.

"we had the cards loaded on the Oyster , picked up the brochure and vouchers , and used them anyway , no one batted an eye . Again , this was only our particular experience , used them at Cutty Sark , Hampton Court ."

I think that you were just lucky, I've seen other reports that state people had their paper travelcards inspected when using the 2 for 1 vouchers at attractions.

Absolutely , you are quite right . That is why I carefully noted that I felt this was a purely anecdotal experience and certainly did not suggest this route as a reliable option .

Advice for you here may not apply to others reading who will be traveling next year.

There are dramatic changes coming to the prices of Travelcards - up, way up; and the daily capping prices on Oyster cards, down quite a lot.

People traveling after the New Year will need to recalculate their maths, especially if they are considering using Travelcards to qualify for the Days Out promotion of the railway companies.

Yes I posted this a few days ago which goes some of the way through this: https://community.ricksteves.com/travel-forum/england/london-travelcard-price-rises-in-2015-some-oyster-contactless-card-caps-fall

Still the old prices for Peggy though for the 7-day as it (just) comes before it.

Thanks everyone for the help! And thank you for the good reminder about the two-for-one deals with the paper Travelcard...I looked at all the offerings, and given our specific itinerary for this trip it doesn't sound like it's worth it for us as we've already done several of the high cost attractions, but I'm sure other travelers will benefit from the advice!
Best,
Peggy