Is outdoor seating possible from April?

I believe its only for special events

The only time I've seen the outside used is for private/garden parties. I don't think it's used as an outdoor seating section.

According to the website, https://www.thewhitney.com/garden, the gardens are open from Memorial Day through Labor Day.

I would imagine it depends on the weather. I would doubt as early as April, but definitely by Memorial day. You may want to call and ask.

Good question