[SML] large group wifi has me spooked

[tech dept]

What do you folk do to prep for large scale WIFI / internet interactive presentations.
In a week I will be involved with a meeting with between 100 and 150 attendees. All with interactive laptops and their smart-phones trying to grab the venues WIFI and internet access.
The venue is served by Comcast and is connected to their fastest service, that they provide short of fibre. 
I worry about being the sole tech person trying to deal with a probable lack of 'sockets' (connection points) and internal bandwidth.
What should I be requiring the venue to do/provide, so I don't get stuck in a corner trying to give answers/solutions to problems I didn't create. Get more access points, distribute channels, place all access points on 'auto'. I am at a loss.
Currently the only WIFI equipment serving the meeting space is the Comcast Cisco modem (2.4 and 5ghz) and 2 TP-link TEW-650AP access points.
I have no plan "B", short of having all attendees use their smart phones data-plan time..
(I will be providing the presenter with a direct fibre link from the modem to the stage)
Thank you

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