I recommend choosing a direct train between Amsterdam and Rotterdam that only takes 40 minutes. There’s other regional trains that make several stops. Anyway, the frequency of trains is amazing, not having to wait long at the station is very convenient. In the train, there are designated spaces for bicycles, wheelchairs, baby strollers and luggage. Unfortunately, some trains during peak hours are too crowded and it’s impossible to find an empty seat. I had to stand for the whole duration of the commute while holding my suitcases, which made the trip a little uncomfortable. Moveover, the restroom wasn’t available and I accidentally took the regional train which stops quite often. All in all, the trip wasn’t very pleasant but I got to Rotterdam in time.