If you do something smilingly, you do it with a smile on your face.
Doing something smilingly is usually a happy and friendly thing.
Examples:
She smilingly waved at her friend.
He smilingly agreed to help.
The child smilingly accepted the gift.
The dog smilingly wagged its tail.
The sun smilingly shone down on the happy picnic.
The flowers smilingly bloomed in the warm sun.