Depending on how many there are, I recommend a chartered bus or a transport service that can take everyone straight to the building you need to go to to minimize walking.
There is parking there, so you could charter a bus if public transportation isn't an option. It is fairly wheelchair and rollator accessible. The pebble floor of the Chinese garden might cause some difficulties with these devices, however. They don't guard the garden so there were kids digging rocks out of the floor and throwing them at each other and running around playing hide and seek. This would be a major hazard for a group of seniors.
You can call a car service or uber and request a van for a group. Or the S44 MTA bus runs from the ferry to snug harbor cultural center. Might be a 5 minute walk to the center from Richmond terrace
Use your GPS
Depends from where, but if on SI, maybe rent a mini van, try Urby, Matamoros taxi van etc
It is easy to get there by ferry to Staten Island and then take the bus. A chartered bus will even be easier. There is plenty of parking.
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