Did you take young kids with you ? or would it be ok for us to take 2 young children aged 4.5 and 8 ? How was the language barrier for you?
ABSOLUTELY you will be fine! We've been to Japan twice. Once in 2006, which was just me and DH, and then in 2010 with our boys, then aged 3 and 16 months.
We both absolutely love, love, love Japan. On our first trip we spent a week based in Tokyo and a week based in Kyoto. We actually didn't see much of Tokyo, as we spent most of our Tokyo time in
Disneyland and Disney Sea. Kyoto though, was beautiful. We did day trips from there to Nara and Himeji as well as exploring the city and going to a J-League soccer game (DH is a huge soccer nut).
On our second trip with the boys, we only stayed for a week in Tokyo and only ventured into the city on one miserable, failed excursion, but that had nothing to do with the city or country, and everything to do with two tired babies, a pregnant mummy, rain and a whole lot of impatience. The rest of the time we spent in the Disney parks and again, BRILLIANT.
Tokyo DisneySea is an amazing park. There is no other park like it. The themeing and just the overall atmosphere is magical. The two combined parks are actually DH's favourite, and very close to being my favourite - although I haven't been to Hong Kong.
The language barrier will most likely not be a problem at all if you only plan to stay in and around Tokyo and if you are only thinking a week, that is probably wisest. I did Japanese in Yr 12, but only remember the basics and some odd phrases like "My car is not old", not really helpful

And we didn't have an issue at all. We had one of those billingual dictionaries which helped us in the few instances we encountered non-english speakers. We found that most people automatically spoke to us in English. We even had people come up to us and tell us how adorable our children were in English
On our trip with the kids we stayed at the Hilton Tokyo Bay. It's on the monorail line (well, a five minute walk from the station) and we found it so easy getting the kids back for mid-day naps. We spent the last night at the Mira Costa overlooking DisneySea and it was A-MAY-ZING. Would love to stay there again, but at $400/night it's a tad on the expensive side. I think we got the Hilton for around $180/night. Try checking out the UK Hilton website, they seemed to have better deals than elsewhere when we were booking.
My kids are notoriously picky but plain eaters so they basically survived on Mickey-shaped nuggets, fruit and sandwiches while we were there. We couldn't tempt them with anything more adventurous. Oh, unless you count the honey popcorn from Disneyland (they also have chocolate, strawberry, coconut, cappucino and some other interesting flavours available in awesome collectable popcorn buckets).
The trips were a bit hard to plan, especially since we were use to the ridiculous amount of information there is available for the US Disney parks. We got it all sorted eventually though, the hardest part to organise was the transfer to our hotel from the airport. We flew Jetstar with the boys and our flight got in in the evening. All the bus transfers to Disney hotels had finished for the day. Knowing this in advance, we organised a private car transfer. We would have gone public transport - which is terribly efficient in Japan, like nothing I've ever seen - but with the two littlies, it was easier to go with a private car. It was a little expensive, but the peace of mind, and having the kids in carseats made us feel a lot better, and I got a little kick out of having somebody hold up a sign with our name on it
Seriously Japan is a GREAT place to visit. DH has been trying to figure out a way to make Japan a pitt-stop on our way to the US on our big trip in 2015
