For night trains : definitely Berlin/Hamburg - Stockholm, there are 2 companies on this route : SJ and Snalltaget.

- Brussels or Amsterdam - Vienna : nightjet.com. Add Interrail as a discount. From Vienna multiple trains to Prague

Most dates this summer are already sold out for night trains so double-check availability.

You'll need to book Eurostar well in advance too.

Some other thoughts : why not take the Stena Line overnight ferry between Harwich and Hoek van Holland (near Rotterdam) ? You get a 30% discount with Interrail (code EURAIL2023) and it is a fun way to cross the North Sea ! (the other way around take the Eurostar). I'm not saying that because I'm doing that exact journey this September... no...

When are you travelling exactly?

Your route is a bit city heavy, you’ve chosen quite convenient rail countries to travel in. So it’s rather easy to dive into nature too.

Brugge-Gent-Brussels is not far, if you choose one “base” you can cover entire Belgium by train. I regularly do hikes from station to station in Belgium, following GR-trails. It’s very convenient if you want a bit more nature and lesser known parts of Belgium, away from the hordes of tourists in the cities in summer (https://www.belgiantrain.be/en/leisure/b-excursions/more/green-stops/by-foot-green-stops ).

If you want to go to Czechia from Belgium, the Nightjet to VIenna is a good option. From there you have good acces to southeast Czechia. Brno, Olomouc,… also well worth a visit, from where you can get easilty to Prague. Best book the nightjet asap.

From Prague, it’s not far to the east of Germany. Zillion options there, to do something. Also a lot of green (like the Saxon Switzerland) on the Czecho-German border.

Also doable by day trains, Czechia, by the way, should the sleepers be fully booked. Although going over Germany will be easier and more direct.

Personally, I think that Stockholm drives you a bit out of course. Perhaps you should leave that for a Scandinavia-only rail trip.

Including Denmark would be very possible to, Aarhus, Odense, Kopenhagen, and much more in between, all very nice to visit and easy to reach from Germany.

If you plan to travel by Eurostar and haven't made the reservation yet, you should check availability for your travel dates and make reservations ASAP.

There is a limited number of pass holder seats on the Eurostar between London and mainland Europe. On popular departures and during high season those sell out weeks, and sometimes months in advance.

The best place to see the availability of passholder seats and make reservations on the Eurostar is 

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

If you don't get any result, press "later trains" and eventually you will find the next available connection. 

If you have a mobile pass you need to generate a Pass Cover Number in order to make the reservation at b-europe. You do that here in the PCN generator:

https://community.eurail.com/news-and-announcements-39/pass-cover-number-generator-is-live-5653

Thanks all

Yes, have been keeping an eye on the Eurostar reservations. Going mid-week around 9th August so a few times left to both Brussels and Paris, but want to book soon.

Appreciate the route is city-heavy, but with the kids we’re quite enjoying the city breaks.

Think you may be right on Stockholm being out of the way. May leave until next year.