Originally Posted by
jib71
Or ... My splurge recommendation ... Get in a cab at Haneda and go straight to the Tokyo Oedo Onsen Monogatari - Hot springs on O-Daiba island. Last entry is at 7:00 am, so you need to get your skates on. But once there, you can soak in a tub for a couple of hours. Depending on your level of confidence, you could try taking public transport back to Haneda Airport.
Definitely what I would do. Much more interesting than temples. If you had time, the giant ferris wheel at Odaiba could be squeezed in although that actually may not open till ~10am or so.
I did not know they closed receptions at 7am (thought they were open 24hrs). If you're able to get on the cab before 6.30am, then I would go for it.
Otherwise just take a little monorail ride then back to HND, enjoy the landside shops and restaurants, and call it a day. The landside facilities are interesting and packs a punch in a compact area, so it'll likely be higher yield for you and your kids than a lot of places outside for that short of a time frame... moreover, places should be open at HND at those hours, unlike most places outside.