Definitely try to go into assisting if you can't shadow, I say. And actually I made more money as an assistant than I would've otherwise. At least in the offices I've worked in, it's been just as good as shadowing and it might give you a little insight to keep in mind when you have to deal with your own assistants later on down the road. Only problem is that not many places will higher assistants for just a few months, since they have to take the time to train you and get you accustomed to that specific office, they usually like to see longer staying power. What I did last summer was work for a temp dental assistant agency. That was even better because I got to see how six different offices were set up and run and how each dentist carried out their procedures. Picking six different dentists brains too was great. Unfortunately there's no promise of work from week to week, so I didn't make as much as I could've with a steady job, and some dentists tend to forget that you're a temp and can't read their minds like the assistant they had for 10 years. But for the experience you can't beat it.
