I'm not TCX but do fly to TFS regularly. From BHX you will either go down a Tango route, or down across Bay of Biscay, track down the Portuguese coast before heading off south west towards the Canaries.
For a sample Tango 16 route see here:
(although many routes head off towards Dublin, down through Cork, and then pick up the Tango)
Runway 08 is the most often used runway at TFS (as has been said) so sitting on the left you will get a good view of the volcano as you track down the west side of the island before turning in towards the runway. Although anything you see will of course always be dependent on the weather at that time!
Nothing untoward about TFS - good long runway, decent vectoring now they have stopped their stupid work-to-rule, and good ground handling facilities.
If you're so interested in the flight, when you get on the aircraft politely ask the SCCM if there would be any chance you could pop into the Flight Deck on the ground and say hello. We always try and accommodate such requests time permitting, and the worst that can happen is they say no!
Enjoy your flights and holiday!
DW.