Instead of doing complex criss cross wood design, just do plain planks, stain light sandy colour and pain on a beach scene or incorporate a printed pic. Give to mom as doggie door (for keep dogs off stairs).
Check out this project on RYOBI Nation - Needed a baby gate for the top of our basement stairs. I took out the existing basement door, and placed a by wooden baby gate. Made from common boards, sanded it down, stained it Golden Oak, screwed it