We loved Capri. If possible, add an extra day or two.
We stayed here https://www.giardinocapri.com Franco is your host. His family has lived here for generations and everyone on the island seems to know and love Franco. He will provide great recommendations for dinners, places to see and things to do.
Regarding the Blue Grotto - there is plenty to see and do on the island.....especially if you are able to walk. We were so busy, we did not have time for the Blue Grotto. And Franco said you will probably get more value for your money by taking a boat tour around the island.