Children are not allowed on the Enterprise in the alternate timeline. While it's never commented on, Wesley is allowed to be on the ship because he's now a uniformed member of Starfleet rather than a civilian with an acting ensign rank. In the "real" timeline, Wesley is old enough to enlist in the first season, and in this timeline, he apparently went straight into the Academy as soon as he was old enough and graduated already. Or, similar to what happened with Nog during the dominion war, he was given a field commission because the war is going badly and Star Fleet just needs more officers.
The opening scene where Guinan introduces Worf to prune juice seems innocuous at first, but it subtly highlights the stakes of the episode: in this timeline, Klingons are allies, and Worf is friendly enough for Guinan to give him dating advice.
Guinan tells Worf to drink his prune juice after he claims he is unwilling to seek companionship with a human crewmate out of concern for their well-being. Prune juice is used to treat constipation, so Guinan is saying he's full of crap.
