The easiest thing (if this isn't too late) is the following. I STRONGLY RECOMMEND that you do all of this ahead of time and test it.
1. Bring your wireless router. Set it to WPA2 (or some other secure mode) with a password only you know. If you have a choice of a router, you'll probably have better reliability with a 5GHz mode WiFi router. However,
all of your mobile devices will also need to support 5GHz mode, and many still don't.
2. You may also want to hide the SSID broadcast, so that people at the trade show don't continuously pound you trying to connect. You'll need to know how to do this with your router, and then how to set the connection up manually on your mobile devices though.
3. Set the router up as a DHCP server and whatnot (basically "normal mode"), but set the MC Server with a fixed address (static). Usually, you can just do this by changing the IP configuration on the
Server machine itself. The address you assign will need to be in the same subnet as the DHCP server on the router (probably 192.168.0.X or something like that).
4. Depending on what the trade show gives you, you may or may not be able to get the "whole setup" on the Internet. If they give you an unsecured Ethernet connection you can plug into whatever you want, you can plug that network connection into the WAN port on your router and it'll provide Internet access to all of the connected devices. Otherwise, you'll have to operate your WiFi network without Internet.
5. Wire that router (via one of the LAN ports) to the MC server, and set it up with a fixed (static) IP address.
6. Connect your mobile device(s) to the wireless router via WiFi. They can get DHCP addresses.
7. Connect from Gizmo or JRemote or whatever directly to the static IP address you picked for your Server in step #3 above.
8. ? ? ? ? ? ? ?
9. Profit!