Hi Katrina - you can probably go without he 64gb - the choice of 16 or 32 comes down to two things:
A. Do you need to have lots of videos on them - either podcasts or recorded with the iPad - if you get the new iPad3 videos recorded will be much larger
B. What lifespan do you plan for them? If beyond 2 years you may want the extra space - I've found that many new apps and iBooks files while packing fantastic graphics etc are larger files (the retina screen of the new iPad 3 also means app files are somewhat larger.
Hope that helps!