Hi
Make sure you have a good map.
You should allow at least an hour to drive to Timanfaya NP from the port. Opening times are 9.45 - 17.45 (for more details, see http://www.turismolanzarote.com/en/centros-turisticos/the-fire-mountains-timanfaya/5464 ). Depending on season and time of day, you could wait up to an hour to get into the park when it's at its busiest (but don't be put off, it's definitely worth it!).
The drive nearby through the wine country - La Geria - on the LZ 30 is stunning and you really should do it either on the way to TNP or on the way back, regardless of whether you're interested in wine. You might want to stop at the Monumento del Campesino - another Manrique creation - for a drink and wander round (it's free).