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.
I would second this, and point out that since your children would be with you the price of the cab vs 3 monorail tickets would not be that outrageously more.
Also, if my geography is correct the cab ride would take you over Rainbow Bridge, with excellent views of Tokyo Bay (a bit nicer than the very industrial/warehousey views on the monorail).