It is up to you to know how many pass days you might need. As Swiss tickets are very expensive it might be a good idea to use a pass day depending on your journey. The 11 y.o. child travels for free but you need to book a free pass + pay seat reservations for them too.

Seat reservations to add (per person) :

- 13€ Rome - Florence

- 13€ Florence - Milan

- 26 CHF for the Bernina Express : the route can be done on hourly reservation-free regional trains (some with 2 open-air coaches in summer, AW symbol on SBB app)

- 49 CHF for the Glacier Express to Brig (very popular, full weeks in advance) but the route can be done on hourly regional trains : St. Moritz - Reichenau-Tamins (or Chur) - Disentis/Mustér - Andermatt - Brig*. Not longer, less crowded and fully reservation-free.

- 9.80€ (for the whole family) Interlaken - Ulm through bahn.com

- 17€ Frankfurt - Paris

- 30€ Paris - London. Book ASAP (limited number of seats)

- 30€ London - Brussels. Book ASAP

- Brussels - Amsterdam use the hourly reservation-free IC train instead of the 27€ Thalys.

- 3€ Amsterdam - Frankfurt. Book well in advance too (very popular route).

For Italy + Amsterdam - Frankfurt use : tickets.oebb.at (no booking fee) -> add Eurail as a discount and select one-way tickets.

Eurostar use : https://www.b-europe.com/EN/Booking/Pass#TravelWish

About Interlaken area : Eurail pass fully valid on boats on Lake Thun and Brienz. 25% discount for tickets to Lauterbrunnen, Grindelwald and above

*another very scenic route to Interlaken (I'd choose this one) : St. Moritz - ... - Andermatt - Göschenen - (every other hour, change in Arth-Goldau) - Lucerne - Interlaken Ost

The good news is that with a mobile pass you generate a universally acceptable ticket for each train on the screen. For the majority of services your reservation (which is separate from your pass/ticket) is also acceptable in either pdf display or as a printout.

You need to add each train to each pass (can be done to all passes in one go if on one device) and then, once activated, a slider appears that once operated creates a travel day and shows a QR code for the day plus a list of each train as you transfer them before boarding. An inspector will check the code and that the train in in the list, plus if there is a mandatory reservation, the evidence of the reservation. You need both for trains with mandatory reservations. 

 

Thanks @thibcabe and @Yorkie for the insightfull and detailed reply! I guess my last question is I was booking on the oebb site and it had this rather large message saying that “You need to print tickets”. I guess my question is, do I really need to print the tickets or can i just show the pdf or email?

The PDF version is good enough :)