HiGinster, we used http://www.officialtaxitenerife.com last February when my daughter was 8 months old. I found the company via the Tenerife Sur airport website and they had a counter in the arrivals area. Would use them again - really easy to locate their counter, English-speaking, car seat already fitted, responded promptly to email queries and turned up on time (with car seat) for return journey. The only thing was that the car seat was forward-facing so depends on how comfortable you are with that for your youngest. If our journey had been longer, I might have looked into whether or not it could be fixed in a rear-facing position (but our flight arrived late and I was obsessed with making sure she didn't fall asleep in the car and mess up bedtime routine - I know, need to sort out priorities!). Good luck and enjoy your holiday!