As the others have said, Ruckus is an excellent choice and a huge step up from Ubiquiti for the kinds of environments you're describing (high density public venues)
What is your goal in terms of the speed of wifi you want to deliver your customers? Of course, one bottleneck will always be the bandwidth of your Internet pipe.
My personal recommendation is instead of buying an older model AP that might EOL soon, buy a newer AP, especially one that supports 802.11ac. You mentioned that you expect the majority of your clients are going to be smartphones and other mobile devices. These tend to be 1 or 2 spatial streams at most, so you can use an AP like R500 which is 2x2:2 and save a lot on cost -- possibly coming close to the price of the 7982 you mentioned. The 802.11AC AP's come with newer generation antennas and electronics that result in better bandwidth, even if your clients are 802.11n only. Plus, a lot of new generation smartphones do support 802.11ac Wave 1, so they will be able to take advantage of faster data rates and occupy less of your precious air time.
The 7372 is similarly a good indoor 2x2 AP, and is the 7982's little cousin. If that fits your budget more, that might be a great option too if 802.11ac is out of your price range.
Since you're cost sensitive, one last pearl of wisdom from my experience is that it's almost always more cost effective to put in multiple lower cost Ruckus AP's than one high end one. For example, if for cost reasons you are deliberating between 1 7982/R700 or 2 7372/R500, I would lean towards the latter. The incremental step up to the high end Ruckus AP's is noticeable as icing on the cake, but it will not be an improvement if it's at the expense of having a single AP struggle to cover the whole area, or having too many clients on one AP.
As far as management, I think for your usage as long as you can run ethernet to every AP, standalone will probably be fine for set-it-and-forget-it. You will need some sort of controller (e.g. a ZoneDirector) if you need to extend your network via wireless meshing or if you need more fine-grained access controls like a restricted guest network. One other benefit with a ZD is that it will cache keys for 802.11r/k fast transition, which may entice stickier clients to roam to nearby AP's more willingly and seamlessly. But again, if the trade off is between getting a ZoneDirector or another AP... you know my thoughts on that!