Hi Lisa,
Well, I'm not surprised your excited - travel documents means it's not long until you travel!
In terms of luggage you can take 2 cases and 1 piece of hand luggage. The maximum dimension per case is 85cm be it width, height or length so there is plenty of luggage space. The only thing you need to remember is that there is no porterage and you will need to carry your own bags. The coach when it meets you in Paris has to park a couple of hundred metres away from the station so a a case with wheels is ideal.
In terms of weight, there is no limit, but please bear in mind that you will need to be able to lift it on and off the train and through the baggage scanners.
I hope you have a great trip!
Kindest regards,
Julia