"Avec grand plaisir" is grammatically correct, but it's a bit more formal and emphatic. "Avec plaisir" is more common and casual, used for simple agreement and willingness.
Here's a breakdown:
* "Avec plaisir" (with pleasure) - General agreement and willingness.
* "Avec grand plaisir" (with great pleasure) - Expresses stronger enthusiasm or eagerness.
So, depending on the context and your desired level of formality, you can choose the appropriate phrase.