I need xfer from orlando airport to port canaveral then back to disney resort for a week. rent a car?

You can get a one way, one day rental for around $70 including the one way extra charges (although sometimes you can get a deal that knocks this extra off). Avis Budget and Thrifty all have depots near the port so you drop off your car at the depot and they shuttle bus you to the ship. When you return just hop back on the shuttle to pick up your 2nd pre booked hire car. The downside is that quite often the shuttle buses are swamped by the number of passengers trying to get on and it can turn into a pushing and shoving match. Allow plenty of time for your transfers and you shouldn't be too stressed out. If you are going straight to the ship from your flight then I would get the Mears transfer to the port and pre book a hire car for your second week.