Absolutely no it won't work. Don't try it. Don't suggest it to your boss. Don't promise that a good solution will be anywhere near the cost of what you're proposing here.
Even the top end Cisco LAP 11xx and 36xx series APs are rated at an absolute maximum of 100 users. To simultaneously support 800 users, I wouldn't use any less than 10 enterprise grade APs (not Linksys, not Cisco small business, but real enterprise APs), with an ideal number between 20-25 depending on range and failover capacity.
You also don't mention how much space they are spread over. You need to plan for capacity as well. If you have one room with a max of 5 people and another with a max of 500 you're going to need to plan accordingly. 800 wifi users isn't a task for SOHO gear. If you want it to work well, buy enterprise grade APs and controllers. You can easily spend $30k+ USD or more for appropriate get to support 800 concurrent users. Have someone from Cisco, Aruba, or any other major vendor come out and do a site survey and capacity plan for you. Wireless capacity and site planning is an art, and you don't seem like you have much experience so you should leave it to the professionals.