Create a simple que for each user with max-limit down at 1024 and max-limit up at 128 and limit-at down at 1024/8 = 128k and limit-at up at 128/8= 16. This way if one person wants to use the network and no-one else is using it then they get the full bandwidth, but if everyone is using the network then each person gets a 128 down 16k up pipe. But pain to create 80 queues manually.
Use hotspot to create queues dynamically.
Set up a PCQ queue on the upstream (to internet) link using src-address and pcq-classifier as IP address. This way each person will get their share of the available link (http://www.mikrotik.com/docs/ros/2.9/root/queue) . This is probably the easiest.
Kinda depends if you just want to equalize access to the network or really want to limit people to their % of the network.