The main issue I find with those travelling with dogs is their tendency to allow them to sit straddling the aisle. Whilst I have no problem with dogs myself, I always think it breathtakingly inconsidrate to expect others moving around the train to have to leap over sometimes very large animals, particularly considering they can pose a serious problem problem for a good few people. Many owners will make absolutely no effort whatsoever to shift their dogs when people need to pass, just arrogantly ignoring the situation as if the animal isn't there. They can also pose a substantial trip hazard, and there is always a risk of the dog being stood on and suffering an injury itself. Presumably the owner would look to blame the poor sod having to negotiate the obsruction in such a situation, rather than acccept that they failed to supervise their pet properly?! Anyhow, my advice would be to book a table, and have the dogs lie beneath it where they are out of the way of others. I'd also ensure you have a contingency in the way of some food and water, just in case something goes wrong and you end up stranded in the middle of nowhere for half the day - unlikely of course, but you just never know!