Hi there, I asked this exact same question last week... for the exact same reason. I didn't get many answers... and the answers varied between 2:30 and 4pm. I think dinner starts in a lot of places at around 4pm, so my money is on between 3-3:30 for the end of lunch, but guess that it varies from place to place.
We are planning on doing our sit down, table service meals at lunchtime, and then doing cheaper counter service meals in the evening... and thus keep the price down.