How much money to put on oyster card

The Oyster card won't cover train trips outside of London, so you just need enough to cover Tube and bus transport within London. And there is a daily cap for tube travel, not sure what it is now but you could find out. You could start with £20 and add more when you need it.

But have you considered the advantages of a 7-day paper Travelcard instead? Those 2-4-1 deals on major London attractions are sweet. You could group your visits to those within a 7-day period to take advantage.

And buy your train tickets to York/Whitby 11-12 weeks ahead of travel to get the discount Advance fares. Where else will you go on daytrips? Might be Advance fares for that too. Or discounted Day Return tix.

I would put £20-£30 pounds on each card (if two of you are travelling together, you each need a card).
If you stay within the central zone (zones 1+2), the "cap" (maximum you can pay for one day) is £7.00 per day (new, 2019 prices) so £20-£30 should last a few days.

Whenever you use the card it shows your remaining balance, put for only about 1 second, you have to be quick.
When that runs out, you can top the up at any tube station, and at many small shops.

Getting to Whitby (Whitney is a different place):
You take a train from London King's Cross to York (2 hours) then a bus. You can go all the way by train, but it takes longer, and the bus route from York to Whitby was voted Britain's most scenic bus route.
See here: https://www.bbc.com/news/business-44226761

Trains London to York, times and tickets here: https://www.lner.co.uk/
Tickets are a lot cheaper if bought in advance.

If you are flying in and out, London Heathrow to Central London by Piccadilly Line, Oyster card is valid. This is not in zone 1 or 2, cost: £5.10 (Mon - Fri, 06:30 - 09:30) and £3.10 (all other times).
Oyster is also valid to Gatwick airport. Other airports are outside the Oyster area.

And London to Paris by Eurostar train: https://www.eurostar.com

They probably will have to go into London to get the Oyster cards. No sense buying extra ones to travel in from the airport. Or maybe the family member can mail them over somthey will have them in hand when they land.

Oyster card is absolutely valid for London City (LCY) airport. It has its own stop on the Docklands Railway (DLR)

I deliberately didn't mention London City as it rarely features on tourist itineraries, and has no transatlantic flights, so the OP is unlikely to be arriving or leaving from there.
The other 3 (of 6) London airports, Stansted, Luton and Southend, are all well outside the Oyster Card area and require a train into London on which Oyster cards are not valid.

Any money already on the Oyster cards when you get them from your family member will still be useable, it doesn't time out. Return the favour and leave a similar amount on at the end.

To clarify..we will also be purchasing an 8 day flexible britrail pass for each of us.

I was just there.
I came into London from Heathrow to Kings Cross, took a tube from there to Waterloo the next day, came home from my cousins in Surbiton the next day, then a tube to my hotel.
The second day I took four tube rides and two bus rides.
That all cost me twenty pounds, and was only two days.
Not cheap, but so convenient.

If you are concerned about your pocketbook, you probably do not want a Britrail pass.

Those 8-day Britrail Passes will cost you $900 for two people ( unless you are completeimg your trip before the end of February). That is more than $100 each day for travel on the train. Looking up Advance fares for some likely trips, I found fares as low as £18 for York, and £9 for Salisbury ( so £18 if you are doing a day trip. So for two that would be £36 for each day's travel, nowhere near that $112 average you have paid for the Pass.

You can reduce your costs even more with a Two Together Railcard, which takes 1/3 off even the low Advance fares. One card for two people costs £30.

Use this website to look at fares and discounts:

http://www.nationalrail.co.uk

Only downside is loss of flexibility as the Advance fares are for a specific train, not changeable.

We were shocked by the price of a Britrail pass! I did a lot of research and buying advance fare tickets saved us tons of money. Plus, we bought a Family & Friends Railcard ( hubby and I plus our 3 kids). The rail card cost £30, but with our first train trip, we saved much more than what we paid for the rail card in the first place. It was definitely worth the extra research!

Buy your train tickets to Whitby asap; as the nearer it gets to travel time, the more expensive they are.
Make sure you have reserved seats.
When I went by train to Edinburgh from London last month, many people stood all the way for 4+ hours as they had no reserved seats.
Also, have a look at the TFL website for London transport.
It's quite confusing, but at least will show you maps of how far the Oyster card is valid for in all the zones in London.

Darryl and Kimberley have not said when they are going to London. If the trip,is more than 3 months away, they will not be able to buy the Advance fares on the York (and Whitby) tickets, as they are not released until 11-12 weeks out.

I don't know why people keep posting "Whitney" (the first one has been corrected). Lola, is that a US spell-checker thing?

• Whitney-on-Wye is a village in Herefordshire
• Witney is a town near Oxford
• But Whitby is a lovely town on the Yorkshire coast, and well worth a visit.

Yep, auto-correct on my iPad is the culprit. I should have caught that; we have been to Whitby and really enjoyed it.