>captive portal which leads patrons to a table-to-table chat system
The unreliability of captive portals across devices aside, they'll make you download some app you'll never use again, or they'll take your email and spam you later.
That is not a “we can’t do it” problem. That is a “they don’t want to do it” problem.
If you want it and you think it is cool you can have prototypes in a day max. Making it usable enough so even drunk people won’t need help using it will take longer, but it is certainly more manageable than the vacuum tubes as a hobby project.
