Well, some things to keep in mind:
With static WEP, you cannot guarantee that your transmissions are private. Possible HIPAA issues if patient data is part of the conversation?
You also cannot guarantee that all transmissions are from authorized users.
If there's any way to put a VPN client on your devices, that might not be a bad idea. If that's out of the question, all you can do is minimize the possible risks by setting up strict firewall rules that block all traffic from your WEP vlan(s) except to the specific servers and specific ports that need to be accessible, and then make sure that your servers are fully patched and configured to be as secure as possible as well.