Train tickets per person

Hi. From our experience last summer...
1. Yes, to tap on and off, each person needs their own card, because that's how the system identifies you. Tap on and off is very easy and convenient.
2. If you are taking a train anywhere within the Netherlands, you don't need to buy a ticket. Tapping on and off is your 'ticket'. If you are going outside of the Netherlands (e.g. Amsterdam to Brussels), you can't tap on and off; in that case you need to buy a ticket.

I am taking a group of four teens, four parents, and myself (9 total)
( from OP's other post)

I suspect the teens may not have credit cards. What is the work around?

In which case each parent gives their teen a credit card (other than the one they are using).

Where do you want to take the train too? If within the Netherlands an off-peak group ticket might be a good deal. For more information and conditions, see the website of the national railway company NS: https://www.ns.nl/en/tickets/off-peak-group-ticket

People on this forum have mentioned that it needs to be an unique device with a credit card. So someone can tap in with an Apple watch, another with a phone and a third with a physical credit card, all using the same credit card number.

You can also download the OVpay app individually. The NS app allows you to procure digital tickets and often shows off-peak discounted options.

Not all credit card are accepted. Check the OVpay website for the latest list. Amex for example does not work.

If you cannot use tap-on tap-off you can still just buy tickets. So for train trips you just buy tickets on line or from ticket vending machines, or if you want from the ticket office.

And this way you can take advantage of offers like the off peek group ticket.
https://www.ns.nl/en/tickets/off-peak-group-ticket

You can have a look at offers here: https://www.ns.nl/en/tickets

You can also buy e-tickets for use on public transit in Amsterdam. In that case you get a QR code that you scan when boarding each vehicle.
https://www.gvb.nl/en/travel-products/tourists

And lastly you could get a OV Chipcard. But the issue there is that you need to have enough balance on them to be able to use them and so you will invariable have some left over at the end of your trip. You can get that back, but only to a EU bank account.
(I went through the process and had to use my Latvian Revolut account for the refund...)

Tap on/tap off is easier. Is it still so uncommon for teenagers to have their own bank accounts and cards?

The potentially tricky bit about tapping in and out with a credit card is that the Netherlands has more than one rail company; I think there are four companies running domestic routes. Some cities are only served by one company, in which case there's no confusion. In a city served by two or more companies, each will have its own fare gates, and you need to tap in at the right one. There will be a logo on each gate.

You can check ahead of time which company you'll be taking by searching for the schedule on the www.ns.nl website. Take a look at trains from Arnhem to Groeningen to see an example of the involvement of multiple rail companies.