Asking too much of my references/when to say thanks?

[Normal]

I'm applying to two (maybe three) schools, and have already been admitted to one for next year (UK school). When initially writing my references, I explained about my career plans and why I would be pursuing the program I was. I'm about to start my application for the other school, and have come to realize that I'd like to apply for an additional program at that school (on top of the one I was initially planning on). One program was something I've been pursuing in order to advance my career, but the other program is just an academic interest of mine that I think is just important to be educated about in general (plus it's related to my undergraduate degree, whereas the other one is not). I don't want to seem wishy-washy or jerk my references around, especially after they have already enabled me admission to one school (which I am very excited about, but that I need to have a back-up for, logistics-wise), and I was wondering if it would just be a huge dick-move to say, "Oh, by the way, I think I'd also like to apply for X as well...".

On a related note, I was also wondering if it was appropriate to send my thank you cards after all admissions processes have been completed or after the first round? I am extremely appreciative of what they did for me, and I don't want to be tacky in how I express that gratitude.

[emmm]

I think it is fine to express your thanks now. If your LOR writers don't already know about your admissions offer, you could send them an update and thank them at the same time. You could also go on to explain why you feel you still need to apply to some more schools. Your references want to help you, or they would not have agreed to write letters for you, but you should let them know that you appreciate their efforts. Waiting until the whole process is finished before thanking them(February or later?) seems too far off, especially if you have good news to share now or if you want them to do more letter writing. You could wait until then to send formal thank you cards, but send emails at least sooner rather than later.