1. Use ferrite beads where the wires enter your controller board and also at the location close to the lcd and keyboard this will reduce the noise introduced due to longer length.
2. If possible use diffrential communication such as RS422 in order to tackle the problem. But in that case your remote keyboard/LCD side part needs to be modified to introduce Diffrential drivers/recievers.

Regards,
Prahlad Purohit