We have some of that, and if I had my way, I'd get RAM and SSD to start. Then I'd probably run 10.9.5. Pretty solid and still supported. Most of the software that clients are using is working fine on it as well.
There are many of those specific packages I don't use or have access to, but check with the vendors and see their compatibility requriements.

BYO stuff is really out of your control. You can only make recommendations to the students there. Just 2¢ worth.

Thanks, Scott, I think perhaps 10.9.5 is the most prudent solution as reliability is the most important thing. If you'll forgive me for getting out my soap box here, I notice Apple has done some incredibly short-sighted things with its iWork apps. For example, presentations created in Keynote 6.5.x under Yosemite cannot be opened by Keynote under Mavericks. Ridiculous. Just because an upgrade is free doesn't mean we are able to use it, as third-party compatibility takes time. </soapbox.> Sigh.

And yes, we already have a decent amount of RAM.

Yes, and that jogged my sleepy brain too - I think Office 2016 requires 10.10 @endor-moon.
If all of them need the new iApps and Office, you may be in a corner there if Office gets upgraded.

Good luck - it's the "fun" part of this isn't it?

For a lot of our clients we're sticking with 10.9 for the majority. Initially it was the 50% boot hang issue, but since that has been resolved we've been held back with 802.1X wifi issues and opendirectoryd bugs.

If you aren't using 802.1X then 10.10 may be stable enough but for most of our cases we have to avoid it if we can.

I'll throw the contrarian view... since 10.10.4 Yosemite has reached a pretty good level of stability (when discoveryd went away and mDNSResponder returned) for most of our clients. That's what we're seeing (boot hang fix, as @davidacland mentioned, made us hold off widespread Yosemite deployment until 10.10.3)). I actually had a school do some benchmarks and the Yosemite machines were faster than Mavericks 10.9.5. Wouldn't go down any version below 10.9.5 due to the lack of security/other updates (Apple typically only supports the current OS and 2 previous ones for security updates, and with El Capitan to drop in the next couple of months or so, that'll be El Cap, Yosemite, and Mavericks)...

Thanks for all the responses. I'd like to be ready for Yosemite and El Capitan beyond it, but the new issues with 10.10.5 have given me pause. Not to mention I watched a co-worker's MacBook Pro completely fail after the 10.10.5 update hanged with "one minute remaining." Robert, you made a good point about benchmarks and Yosemite. Perhaps I will try Yosemite for our Computer Commons, which is where any students in the place can use the Mac systems, while leaving 10.9.5 in the labs for now. Thanks Scott, I was aware that the new Office 2016 requires Yosemite but I'm not sure why. Perhaps Yosemite is making some things easier for developers?