We are going to Tenerife on Iona in March and the observatory is offered as an evening excursion. For us it was a toss up between that and cable car to top of Teide.
Lanzarote we are visiting Manrique's house made in the lava tunnels. It is offered as an excursion, but should be easy in a taxi as it is close to the port.
I haven't been inspired by anything in Gran Canaria yet.
There is an evening excursion in Lisbon but you have to make your own way back to the ship. It doesn't look far, but there are two of us. You may not want to do it on your own.