On the wedding night of a kallah who is a niddah and a shomer child is needed to stay with the couple, is that also necessary when staying in a hotel?
Yes. It applies to any place that the couple may be secluded. When the couple are going to be in a hotel for the night they will need two separate rooms, or two children sleeping with them. The reason for this is, because there is a need for a two shomrim at night, since one shomer may fall asleep.
Rema E:H 22 – 5