I'd put a dark binding (the green to match one of your borders) on it and leave it the size it is. If this is going to a nursing home, it is very usable with the size you have. It could be put on a bed to add a bit more warmth to cold feet or over a lap while seated. It's already a bit too big for wheelchair use. I think the more borders you have, it diminishes your center design.
Since this is square, you don't want it to be so big that it is cumbersome. After all, bodies are rectangles, not squares!

My personal preference would be to add two more borders of the borders you already have, to me would make for a beautiful quilt. It would be in keeping with an even flow of color. Whatever you decide I am sure will still be a beautiful finish and someone will be very happy to have.

Thank you everyone for your suggestions. All are good and helpful. I'll be sure and post a pic when I'm done, which hopefully will be this afternoon. This forum is the best for helpful and encouraging ideas!

Squares actually work well ... not sitting square on you, it does give you more coverage, IYKNWIM?

TBH I am a square quilt lover ... never have to find the long/short edge!
Having an antique bed with footboard, I don't need a drop at the foot, and not much to tuck in at the bottom. What I need for drop on the sides of the bed, balances with the extra I need for over the pillows. Even as a lap quilt, I love my squares! :)

I really like that green fabric you chose for another border.

Thank you all for your suggestions. I combined a couple and this is what I came up with. I can't believe I didn't think of adding brown until it was pointed out. It measures 63" square -- just perfect for snuggling in.

That is perfect!

Nicely done!

What she said! I like the green, leafy fabric with your top but think a wider green border than your last sunflower border would
set it off nicely.

@Belfrybat your finished top looks great! Perfect fabric choices! (Trying the tag thing that wesing explained)