Hi BHB. Hope the experience is turning out as good as you hoped.
I'm pretty much in sync with Pika's suggestions above. Seki is nice for an amble but probably a little boring for a whole day by one's self.
I would suggest they head up to Nagano City for the day and check out Zenkoji Temple. It's not difficult to find.
If they want to do some shopping for the day go to the Wing Market / Jusco area. Get a train to Takada. Then catch a No. 6 bus or taxi. Wing market and Jusco are about 15 minutes walk apart. Jusco is probably the best start then walk back to Wing Market if time. Alternatively catch the train to Kasugayama (one stop past Takada) then walk for about 20 minutes. Look for the arch bridge across the river - that will take you almost straight to Jusco.
Ask at the hotel if they have a courtesy bus that will take you to Seki or otherwise ask them to call you a taxi. The taxis all have ski-racks at this time of year so you'll all fit in one. Can't tell you the fare (sorry). They will probably have to go back to the main road and back up again to SO.
You can get the train to Sekiyama (one stop from Myoko), then a bus (schedule here -
http://www.marukei-g.com/busgroup/rosenzu/seki-tubame.pdf) but that would be more hassle than it's worth.
Good time to go. They have about 300cm base there at present
