Jet lagged with young kids, what to do on arrival?

We will be coming off a long flight, arriving in the morning with a baby and a preschooler. Any ideas for gentle activities that day and ways to deal with the jet lag? We can leave our luggage, but won’t be able to rest in our Airbnb til at least 2-3pm.

Usually I’d hit a day spa or book a massage, but would a public onsen be doable with young kids? If so any ideas around the Umeda area?

by y_if