You're better off on foot, in sensible shoes, exploring the narrow, winding, steep cobbled streets and magnificent views from the breaks in the high ramparts and the vast terraces at each level.
There are three official routes around Dalt Vila, though you can just wander around, get lost and surprise yourself at what you find. The tourist office in Vara de Rey gives out free guides to navigate the warren of streets and there are information plaques sprouting up from the ground all over; these give you, in multiple languages, a chance to learn and do your own guided tour at your leisure, amidst the residents hanging out their washing from their balconies.
A fantastic way to discover the hidden treasures of the old town are the guided tours by Ibiza City Tour - the experienced guides will stimulate your imagination with many anecdotes and interesting facts. https://www.ibiza-spotlight.com/ibiza/daltvila_i.htm
Acrobosc Ibiza is a fantastic outdoor adventure park with activities both for young and old. Set in an area of pine trees just 100m from the Cala Pada beach, there are three circuits you can follow, according to your height and age, putting your balance and skills to challenge. Thirty-nine platforms between 2 and 6m high, 49 obstacles and 20 zip lines from 4 to 65m length and trampolines will guarantee you 2 to 2 1/2 hours of fun & adrenaline.
After fitting you with a safety harness, the instructors will train you and then it's up to you to find your pace as you balance tight ropes, walk over nets suspended mid-air or slide down one of the zip slides (always safely connected to a safety cable). Those under age 18 need to be accompanied by an adult. https://www.ibiza-spotlight.com/activity/acrobosc-ibiza