A good starting point would be the website of the Spanish airports authority:
http://www.aena.es/cs...2871783&pagename=Home
Use the drop-down menu, at the top left, to select the relevant airport, and click 'Go'.
On the next page, click 'Vehicle Hire' (towards the bottom of the centre column of text).
You'll then see a list of all the car rental firms serving that airport, together with links to their websites.
Those links will then show you what's available.
You'll probably need a Mercedes Vito, Volkswagen Transporter, Fiat Scudo, Peugeot Expert or similar. (They all seat 9, with space for 5 suitcases).
Chris