Well first WEP and WPA are not the same. WEP is the old WPA is the new standard. But this has nothing to do with Disney's High Speed Internet Access (HSIA.)
If you bring your own router (I carry a Apple Airport Express Basestation, for travel) You plug that in you room, and it does Network Address Translation (NAT, also call Masquerading) so everything "behind" the router shares a single address.
At no point is Disney involved with your WPA network. No reason to change your password. So I'm really not sure what you are talking about.
The HSIA that is provided at the resorts (which isn't really on Disney's network, one of the local ISPs does it) they provide you with a private IP address (out of RFC 1918, 10/8 space) so as long as your router doesn't give out a 10/8 address you should be fine (most home units use a /24 out of 192.168/16.) I know the Airports detect that the addresses are being "Double NAT" and warns you.
For what it's worth Disney seems to use 802.x certificates for wireless access to their networks.