You've said that your students are at a "university" (i.e., not a community college), and have clarified that they're in the US. Your characterization is that "most of" them find a standard textbook not "accessible," or "unreadable."
It's unclear what you mean when you say that you want to cater to "English language learners" but "most of the students are Americans." ELL is a term used to mean people whose native language is not English. Given your student population, it sounds like probably the majority of them are not people whose native language is not English.
Terms like "unreadable" are absolute, whereas reading comprehension is relative.
You cannot guarantee your students the ability to benefit from a college education. All you can guarantee them is college-level instruction that is appropriate for students who have the preparation and motivation to succeed in college-level work. You can also, if you choose to do so, guarantee that none of them will be limited to a second-class education by the structure of your class, or held back from improving their academic skills and critical thinking ability because the class is taught at an inappropriate pre-college level.
Currently, I am essentially wasting my students' money since their books are unreadable to them.
If money is the issue, then choose an OER text. There are many such texts to choose from at the lower-division level, especially for freshman calc.