Regarding applying to both med and vet schools, here's how I look at it. They're both medical professions, each with unique pros and cons, and challenges. What attracts me to both medical fields is the thought process behind medicine--putting together the symptoms in front of you, the history, together with your knowledge to make a diagnosis and treatment plan. And of course, they're both "helper" professions--either way you can truly make a difference in the quality of life of people.
The pros of vet--I think school would be a lot of fun with well-rounded, caring students, great variety in practice options, the wonderful clients; cons--financial, challenging to diagnose (your patients can't verbally tell you where/when/how it hurts, etc.), the not-so-wonderful clients, treatment options often financially constrained by client, hard to get residency positions.
The pros of med--the wonderful patients, usually lots of diagnostic and treatment options, financial, residency pretty much required; the cons--the not-so-wonderful patients, dealing with insurance hassles, the gunner med students (really--the biggest con to me going to med school is dealing with gunners who are just there to put an intellectual/social notch in their belt!).
Personally, I think applying to more than one professional program is more a sign of being open to career possibilities than being "tracked". Is it really any different than applying to a prof program AND a grad program, or law and MBA?
Right now, I have gobs of veterinary experience--I've seen most sides of the profession (sa, la, emerg, research), so I have a really good idea of what to expect and how I'd want to practice. I'll be doing an intensive medical experience starting this winter--with hospital rounds, history taking, psychosocial, etc., to see if I really want to do that. I really feel I'm at the point where I need to do *something*--I'm giving myself two app. cycles to make it happen, then on to something else (probably nursing). Not giving up, just being realistic.
And the thing is, none of us will ever *really* know if our chosen profession is the right one for us until we're out there doing it! There are gobs of people changing careers mid-life, including LOTS of doctors--MDs and DVMs.