WPA/AES to Wep128bit

I have eneed to down grade our wifi security from WPA/AES to Wep128bit
Because some clients are not capable of WPA.

It is giving access to a domain so standard security for authentication is
still in place for domain.
I don't expect any driveby scanning but you never know, its not a high
profile network so it wont be tageted.

Whats your feelings on using WEP 128 bit for client logon ?, secure enough.

Regards
Don