Lanzarote isn’t that big, just be prepared for wind, and make sure you use sun screen. Climbs aren’t ridiculously steep, but make sure you’ve got a few longer rides in before going.
I’ve signed up for the Mad Manc in May – 203km and 3000m of climbing. I can do 8 hour days on the MTB back packing, so not too worried, and can rattle off 50 miles road rides within 3 hours. I just need the weather to improve to get the distance in.
How often are you riding now. I commute 3-4 days a week by bike, 20 miles a day, plus weekend rides.