For the first question, I'm drawing on a number of resources with increasing difficulty. At the easiest level, I am making the stories my classes have co-created available on my student website along with embedded readings (and audio recordings) for them. It sounds like a lot of work, but if each class only has one story or so per week, the payoff is huge because I end up with four original stories of similar proficiency levels along with embedded readings. The students are doing all of the work to create our stories and the illustrations - I'm just organizing them and simplifying them for the easier levels! And, in future years, all of the past stories will be available for additional reading. Our class story library will be HUGE, at an appropriate level with increasing difficulty, interesting, and I don't have to pay a single penny to build it.
There are also a number of other resources available, such as some readings I have personal access to. For example, I do have a few students who are advanced enough to begin reading Martina Bex's weekly "Mundo en tus manos" Newsletter. I organized this along with other reading materials into a Google Drive folder. I also included in the folder Bryce Hedstrom's reading log information, including why we read, how to choose a book, and useful reading strategies (he also has novice-level handouts for free on his page!). Finally, they can check out novels from my class library.
For the second question about how to hold students accountable, I found another use for our Google Classroom! I set up a weekly assignment with the requirements to read 30 minutes per week (my students are novice 7th graders, so I felt this was a good place to start) along with a Google Form that they fill out to receive credit for their reading. They must include their name, the date, the title of what they read, the number of minutes they read (they can get 1/4 extra credit point for each extra minute they read), and a brief summary of what they read in English. Why in English? First, it makes the reading less painful. Second, it's backed up by research. Dr. Mason did a study where students summarized their reading in a cloze format, L2, and L1 - and the students who summarized their reading in L1 actually wrote better in L2 than either of the other two groups even though they'd never written in L2. It's also important to note that I'm merely holding the kids accountable for their behavior (reading something with the intent to understand), but not assessing their comprehension through artificial questions. The students don't need to prove that they gained any particular knowledge, but rather just show me that they are getting the input that they need.
I'm launching my reading program next week - I can't wait! I'm hoping that I've provided enough free choice so that students can find something at the i-1 reading level AND something that they find interesting. I will be sure to report back!