So far, we have been lucky, the big fountain has always been on when we've been there.
We watch the show from the top of the lagoon, then meander over to the fountain and let him go wild for an hour while we sit and chat. Usually by that time the crowd has thinned considerably. We just carry his PJ's with us, along with a towel, and put him into them when it's time to go. We have him brush his teeth in one of the restrooms, then plop him in the stroller and stroll right out the gate, though in our case, the gate in question is usually the IG, which is absolutely deserted that long after the show ends. He's always asleep in minutes.
Unlike the resorts, the Boardwalk is an entertainment area, parking there isn't timed, so if you want to drive and park there, you usually can, even use valet parking if you want to minimize the bother. As a courtesy, we make it a point to park well at the back of the lot if we are not staying there, so as to leave the nearer-in spaces for the guests at those resorts.
For those staying at CSR, the IG strategy is especially good, as there is a dedicated CSR/Boardwalk bus. (Well, at least there used to be.)