@Matchacatta I'm trying to think of relevant things, but the only furcon I have been to has been outdoors (Wild nights).

A battery bank is always a good idea, make sure it's one that supports QC (a lot of the cheap ones don't supply enough power for modern phones) and that you have a good long cable. That way you're not stranded with a dead phone with every available outlet already taken.

Don't forget to tell your bank that you're going out of town, that way they don't disable your card for suspicious activity.

I would say some quick meals too, food can be expensive and you might get hungry with low social battery.

Depending on the hotel wifi policy, or if you just want some additional security a travel router might be good to have. If the hotel makes you pay by device (usually business hotels), this router can be "the device" and it will let you connect everything else. It can also do VPNs including Tailscale if you don't mind leaving a PC running at home as the endpoint as a free option.