I've stayed at several of the hotels which are connected to the convention center:
Hyatt Regency Orlando:
https://www.hyatt.com/en-US/hotel/florida/hyatt-regency-orlando/mcoro
9801 International Drive, Orlando, Florida, United States, 32819
Rosen Centre:
https://www.rosencentre.com/
9840 International Drive, Orlando, Florida 32819
Rosen Plaza:
https://www.rosenplaza.com/
9700 International Drive, Orlando, Florida 32819
I go to conventions which run for several days. I stay in the hotel for which the convention has a block of rooms. The convention center has different sections; the closest hotel will depend on the section. The convention center website's event calendar should tell you which section your event is in, if the convention didn't tell you:
https://events.occc.net/
This map shows the different parts of the convention center and where the hotels are located:
https://view.publitas.com/orange-county-convention-center/convention-center-district-map/page/1
As to whether you should stay near the Magic Kingdom or stay near the convention center: I guess it depends on timing. Do you have to be at the event early (meaning you want to stay near the convention center)? Will you be too tired for a long drive/ride after the party (meaning you want to stay near the MK)?
It's about a 30 minute drive between the convention center hotels and the Transportation & Ticket Center (which is where you would need to park or be dropped off if staying near the convention center).
Let me know if you have more specific questions.