The 'Best of Lanzarote' tour is excellent and worth it. Take the ship's tour because only buses are allowed into the park's interior. This is as close to being on the moon as possible. When the Timanfaya Park ranger pours the surface gravel into your hands from a shovel and you drop it because it's too hot you have to marvel at this planet of ours.
Santa Cruz de Tenerife is probably the only place in the world where you can go from sea level to 12,000 feet in a few miles. Hire your own taxi by getting together with others. You will get to the cable car ahead of the tour buses. Dress warmly because it's below freezing on top of Mount Teide, Spain's highest mountain. Also the air is thin at that altitude if you have health problems.
On Madeira the tallest cliffs in the world accentuate the breath taking views. The lush, green landscape is in sharp contrast to the barren Canary Islands. Hire a van on-line for a 4.5 hour tour including Nun's Valley and to the start of the toboggan ride, a 2 Km down hill ride in a wicker basket. Your driver will get you there ahead of the buses and pick you up at the bottom. We organized 7 people with a cost of EUR 20/pp, much cheaper than the ship's tour. This is the only island to which we would return to spend more time.