I live in florida so we dont fly in, but our family does.
This is what works best for them.
At OIA they rent a car and drive to Cocoa beach, about an hour.
They stay at the Radisson hotel which is clean and moderate priced with a nice pool and a kiddie pool to play in. It is an older hotel but only 4 minutes to the port and is clean and has sleep number beds.
food is good at their restaurant, but across the street is a McDonalds which kids love and also about one block away is an italtian restaurant with great pizza. a couple blocks the other way is a mini golf and go cart place. small arcade for teens if they want to spend the money.
sorry I dont remmeber which car agency they used but they returned the car after they checked in at the Radisson and walk to the hotel and then the radisson has a shuttle to take them to the port and pick them up again afterwards. spend the night there and then pick up the rental car again to drive back to OIA to leave.
I'm sure you could google car rental agencies on line and figure out which one is closest to the hotel.
Radisson.com is the site for the hotel.
Hope this helps some,
That way they dont pay to park the car at the port, save $12 per day.