I realize your post is a little dated but hopefully this will be helpful. I have been working in veterinary technology for over twenty-five years less a couple of "sabbaticals" working with two-legged patients. It has been very challenging being a primary breadwinner and staying in this field but I always find myself coming back to it because career-wise veterinary medicine is my first love.
Most on campus veterinary technology programs are closed programs requiring an interview and having a very finite number of seats available. I imagine the PTA program would be similar and I doubt LaGuardia would allow the dual enrollment, but even if they did I think you'd find it pretty challenging to do your best with that type of course load.
If you truly want to work with both human and animal patients I'd pursue a career as a physical therapist and get a certificate in veterinary phsical therapy. There are a couple of certificate programs available, the better known of the two is at the University of Tennessee.
State laws vary (and will probably be in flux for a while) on whether you can work on veterinary patients with or without the supervision of a veterinarian and at what level of supervision. While certificates are available to PTAs you'd still have to work under a PT and I'm not sure there are enough paying clients available to supporta a PT and a PTA.
Whichever you decide, you're young, I'd suggest you first get some volunteer time in both types of practice and see what you're in for. Then if you decide on one go for your doctorate (or MPT if that's still an option). I can't speak for PTAs but VT is not a step towards becoming a veterinarian, it's a sidetrack.
Life happens while you're still making plans and life's responsibilities are cumulative in nature, the less responsibilities you have the easier it is to be successful in school.
Good luck with whatever you choose.