It's less tricky than you think, but you will want to consider how you approach this, for sure.
If you see that the situation will lead to sex, definitely say it.
They could've assumed you were seeing other people, and continued doing so as well to "even" out the situation.
What is your purpose for dating multiple people? The arrangements are surmountable with all the features offered by Disney, yet Debbie quickly has established the logistics of transportation as well as the overall features of all the Disney properties available that would meet the needs of her clients.
If the one person you're seeing is also seeing other people, it could be that they don't want to be in a relationship.
But that dating more and, with dating multiple.