One option of renting a car at malaga airport and just using it to get to the resort with bags and then return it to the office in Puerto Banus, Marbella the next day. You can get a car for around 35 euros. Then maybe just one person has to suffer the coastal bus. Perfect that you arrive early as car rentals at malaga can take from 2 minutes to 1.5 hours to get car! Sunday is the UK charter arrival day, but more of rush at night.

http://www.arrowcars.es/index.php arrow cars is an agent and has negociated rates with Crown and others.

http://www.aurigacrown.com/index.php

You have avis for return at the Shell station at Puerto Banus, Hertz near the Repsol station in Central Marbella along with Europacar.

They are opening a new shoping walk accross from Gibraltar entrance in La linea and a return there would be possible as well with bus to Estopona.

Taxi AGP to Marriott would be around 75 euros + toll.

Taxi from Marbella Bus Station would be about 30 euros. Highly recomended to not take bus to Marriott as you would have to cross motorway and it is not considered easy to find the first time. If you are in rental car there are many signs, but some get confused when having to re-enter motorway to again exit for Marriott access.

Train Station is renovated now and full shopping center but most closed on Sundays still in Andulucia, Madrid is now just 2.5 hours with AVE train from Renfe Train Station.

Shopping Center Plaza Mayor near the airport has just been doubled in size, but only 40 restaurants and entertainment open on Sundays.