I would suggest that you ask them now. No time like the present. At least they won't need to feel rushed to meet a deadline in the next week or so. I asked my LORs back in May last year and I did not have the PharmCAS ID. I just asked them to do it for me and I would provide them with the other necessary info for submitting it once available. Worked out fine for me.
My application was submitted the end of June and all required docs were submitted early July. It would be in your best interest to remind your LORs occasionally to have it done for you. However, you don't want to be a pest because ultimately they are doing you a favor and not the other way around. Plus, you want good recommendations, not bad ones.😉