I use ptonthenet.com.
I can send workouts with instructions via email, and I can customize the amount of detail and the instructions. I also like that I can use one of their pre-existing templates or start with an existing client’s program and customize it so that I don’t have to start from scratch if I have a client with similar needs / goals as an existing client.
IDEA has a Workout Builder option that allows you to create workouts–exercise by exercise–for your clients (in a video format). I use this with my clients and they really enjoy it. I see that you are ACE certified, and ACE also offers wonderful options in their exercise and fitness library. You may want to take advantage of both options. I’m sure others will have more suggestions, but those two are really good, quality options.
Hope this helps you!