Sounds like a wonderful trip. And entirely possible with the time frame you've alloted for each park. However, Canyonlands is a very large park with two different access roads. I suggest you focus on the northern district known as the Island in the Sky. It is closest to Arches NP and will be more convenient for heading further west towards Bryce Canyon NP. Take a look at the following website for information relevant for the day's drive from Canyonlands NP to Bryce Canyon NP; http://www.brycecanyoncountry.com/ especially regarding Scenic Byway 12.

As for your fear of heights, this trip will involve some curvy mountainous driving but not much. But possibly more difficult for you will be the overlooks from which the most spectacular views are seen. In particular, the views in Canyonlands NP and Bryce Canyon NP (not to mention the Grand Canyon NP if you opt to go there). Of course phobias are not necessarily based on rational fears therefore as I don't suffer from a fear of heights it is impossible to advise you. Most overlooks are well protected with guardrails. And you can approach them as closely or stay back as far as you would like. All of the infrastructure around the most visited overlooks are designed to keep you well aware of the canyons' edges. Unless you have a very extreme case of height phobia I think you can bear it. If you are still uncertain ask amongst your relatives and friends who are aware of the degree to which you suffer, perhaps one of them has visited the area and can advise you accordingly.

Good luck, John in San Diego