Seems to be readily available at Best Buy and probably other retailers. May just be an Amazon thing. The Ultimate version comes with the original Spider-Man game, so if they already have that, you can save $20 with the regular edition.
And of course, you can always buy a digital copy from the PSN store.
As for games, the true exclusives that I’ve enjoyed most are Demon’s Souls and Returnal, but they’re both punishing enough that they might not be ideal for a "family recommendation. Ratchet & Clank is safer in that regard, though I haven’t played it yet.
Plenty of cross-gen or PS5-enhanced options are worth looking at as well, as long as they haven’t played the previous version. Nioh 2, Ghost of Tsushima, Final Fantasy 7 Remake, and Sackboy are the standouts here to my mind. And yes, the PS+ collection is a good way to check out a selection of what you missed from the last gen.