Finkface

The kayak rental company will provide you with the permit to enter the bay. You can NOT land at the monument but you can snorkel right in front of it. It is a very strictly enforced regulation that you may not land on the monument. Only certain tours are permitted to dock on the monument itself. With a rental, you just enter and exit the water directly from your kayak. Just tie the mooring rope from your kayak around your ankle so your kayak stays with you as you snorkel. So yes, you can access the water from your kayak but you can not land anywhere.

Edit: one more thing. That is quite long day to drive from Mauna Kea, sort out your kayaks, spend the day paddling out to the monument, snorkelling, paddling back to return kayaks and driving back up the coast. Kealakekua is in South Kona. That will be a long, tiring day.