I'm in the UK and I must admit I do find it a little boring but generally I think it's perceived as an ordinary name. I know three people with children named
Poppy. I also used to know two adult Poppys who would be in their 50s and 80s by now. I can see it working on all ages although I can see why people think it's a bit juvenile. It's not a name I'd use personally although I do like the flower. Poppies are very much a symbol of Remembrance Day in the UK and one of the girls I know called
Poppy was born close to Remembrance Day. Another friend has a daughter born on 11th November and gave her the middle name
Poppy for this reason.
No one in the UK uses
Poppy as a name for their granddad so that's not an issue.