They would play 2 tomorrow if the second game is necessary in order to determine seeding vs. Reds. If it turns out after the first game that the best the Reds can do is tie us, they won't play the second because we already have head-to-head vs. them.
So as long as the weather is good tomorrow, it's relatively straightforward, the interesting question becomes, what if they are unable, due to weather, to play one or both games, and one or both are still meaningful. Play Thursday?