Oh, I was just in Japan recently and it was fantastic (as always)! (Shirakawa-go was the absolute highlight of my trip, of course.) Kyu-Furukawa Gardens is the name of the real Rokkenjima, and these are the directions to it from the nearest station. Nishigahara Station is only about a ten minute ride from Tokyo Station, so it’s very convenient to get to. As you can see, unlike Shirakawa-go (which requires up to a 4-5 hour trip, and getting up at ungodly hours ) Rokkenjima is easily accessible and actually in Tokyo, and thus doesn’t require a day-trip. Speaking of, if you haven’t heard of the website Hyperdia, I highly recommend it since (because the trains in Japan run so perfectly on schedule) it’s indispensable for knowing how long it will take you to get where you want to go, and how.
Of course, Shirakwa-go is more than worth it too. It’s actually amazing how much local history and local folklore influence Higurashi. (Especially look into Furude Shrine’s history, they have a museum and everything there.) Also, my advice is to head in a bit further once you reach the lookout point, because the really good view is past where most people take their photos. Furthermore, when visiting Furude Shrine, make sure to leave an ema. Seeing all the Higurashi art is really quite neat, especially when there’s quite a few really nice ones that made my crappy rena doodle look extra sad as a result.
Oh, and finally, according to the Japanese national tourism organisation there’s supposed to be a Higurashi monument around, though I didn’t get to see it myself (and I spent ages looking too.) The only thing I can really find out about it (outside of the mention in that article) is it’s probably the lifesized statues of the club members that you can see a picture of on the wiki, but I’m not totally sure. In any case, if you do manage to find it, make sure to take pictures and tell us where it is because I need to know!
Oh, and the gyudon in Shirakawa-go is to die for.
Anyway, as for anime goods, I can’t really add onto what other people have said. Akihabara is the main place to go, with animate and such as the big hitters but even then those are mainly focused on newer anime stuff… If you’re looking for events, the shopping mall attached to the station tends to have something on, and a lot of arcades and figure stores run limited time lottery for exclusive figures and such but… There’s a reason that Nakano Broadway is noted a lot. That said, if you want drama CDs or OST or the like, most CD places in Akihabara have a specific section of the “game cd” or “anime cd” sections just for higurashi.
Congratulations on your honeymoon, by the way. Hope you have a great trip