I thought I would update this thread and give feedback about our day trip.
Things went very smoothly. We purchased a Me-guru one day bus pass in order to get around yesterday. We only used it for two bus legs, but it got 60 to 100 yen admission discounts at the two places we went to, the Toyota Techno museum and Nagoya Castle, so it paid off. A slight bit cheaper than the subway, and when we used the bus in midday, the traffic wasn't bad.
GC3, my wife and kids were very happy with the textile part of the museum; I preferred the automobile portion, but we had to rush through there... The Technoland exhibit was also fun.
We spent little time at Nagoya Castle, mainly because we were so so so hot (it was between 1 and 2 PM).
The Sumo part of the day was superb. We had to go to several booths in order to have our special family box voucher exchanged for our box tickets, but a friendly (and English speaking!) usher walked us outside to the specific will call window we needed, to retrieve our tickets, get us our complimentary souvenir charm (we would never have known that we were entitled to one), escort us to our box, take food and drink orders (the cold beer tasted very very good by the time we sat down), and deliver our food (we got two bento boxes for the four of us, and @2500 yen apiece, I would not recommend it -- the quantity was there, but not the quality). The guy three boxes back who had one (or eight, maybe) beers too many provided much amusement for everyone around. And the matches and environment were great. I speak some Japanese, but my family doesn't, so I had planned to rent the radios that I had read about that broadcast the English NHK "play by play," but unfortunately, they weren't available.
We took the subway back (the Me-guru bus ends service early, and besides, even if it were running, the queue would have been ridiculous). The lines at the ticket machines at Shiyakusho station were long, and many passengers had no clue how to use them. Fortunately, we had no problem negotiating them. The trains were packed, though. I make it a point to avoid rush hour trains in metro areas, but we didn't have a choice here, so it was very uncomfortable on both legs of our trip back to Nagoya Station. Sumo ended at 6PM on the dot, and we arrived at Nagoya Station at 635PM. We had reservations on the 724PM Hikari back to Tokyo, and we tried to change reservations to an earlier train since we got back so quickly, but the ticket queues were too long, so we ended up having ramen and gyoza at a Station restaurant (which was a nice way to get a load off our feet by then).
Sorry for the gory details, but I figured some people would be interested in them...