Does there need to be a fume hood with acetone?
Unless you're using very large quantities of it or in a confined space, usually not. I've spent a fair bit of time washing glassware out with acetone at the sink (using a bin to capture the runoff for transfer to a waste container) and I never had issues. Though I don't recommend doing this yourself, I've also had several errant splashes directly on my skin when working with stuff from the hardware store--again, no problems.
Acetone is staggeringly nontoxic: the NIH suggests an 8500 ppm EEL, meaning that in emergency situations, it's considered acceptable to breathe air that is nearly one full percent acetone for up to one hour. Hell, the air in my house contains less water than that sometimes.
If I can get a ductless fume hood, what am I looking for to be sure that it can effectively take care of the acetone problem?
Look at this link. If the acetone is heated in the box, you should be able to meet all the criteria for being able to use a ductless hood:
A limited number of different chemicals should be used.
Acetone only. Check.
No extreme heating should be carried out in the hood, i.e. acid digestion applications.
You only need to boil acetone. That's 56C, not even close to the boiling point of water. Check.
Modest chemical volumes should be used, around 500 mls or less per chemical.
Even if you need more than this (you shouldn't, 500mL of acetone is quite a bit), it'll mostly be sealed in a box, so you shouldn't have nearly that much escaping into the hood. Check.
Moderate chemical exposure times should be maintained.
I don't know exactly how long it takes to smooth a print, but I don't think it can really be more than a few hours. You're probably okay on this one.
Will the chemicals involved in your application be effectively filtered with the available carbon filters?
Yes. Acetone is so common I can all but guarantee that every company will have a filter that can capture it (probably whatever is used for other general organic compounds as well). In Labconoco's case, that's the organic vapor filter.
How often will you have to replace your filters?
I don't know, that'll be your club's responsibility.
Finally, make sure someone doesn't get the idea that the hood will stop all fumes and try to do a perchloric acid experiment using that hood--that will go badly.
Now, all this being said...
What you really need isn't to make this safe, what you need is to convince administration that you're doing things safely. This may have nothing at all to do with whether things are actually safe or not.
At my old school (where I was briefly president of the local ACS chapter), I could have put an experiment into a fume hood with no filter, not plugged the thing in, and gotten an okay from the administrators because they believed that fume hood = safe and no fume hood = unsafe no matter what else was going on.
I say this not to encourage you to try to trick your way out of this, but to point out that, unless your administration is scientific (i.e. actually understands science), then it's fairly likely you're going to have to jump through a few silly hoops in order to satisfy them.
Best of luck!