The challenge I have found with a tandem is the need to change platforms or cross bridges at stations.
Hopefully a lift is available and the Bike Friday tandem we use for travel abroad is shorter that large wheel tandems which makes fitting in lifts easier.
Also, we caught one train in Holland last year that only accepted single bikes or folding tandems. We said our tandem was folding and would break-apart to form 2 bike lengths. Fortunately, it just fit in the space owing to the small wheels reducing overall length.
I took 26" wheel tandem and trailer abroad once and it was a challenging as the overall length was 4m or approximately the length of an old Vauxhall Cavalier Estate. Quite a beast! Had we needed to use a lift, or transit stairs, we would have had to do separate journey for tandem and trailer.
Challenges are not insurmountable, but they may be there; forewarned is forearmed! Sounds like a great adventure!