A carved pumpkin starts to soften after three or four days, so carve in the last week of October, not the first.
Scrape the inside walls thin where the face is, so the light shows through, and wipe the cut edges with a little petroleum jelly to slow drying. Keep it outside or somewhere cool until the night.
Battery tea lights are safer than candles and do not cook the lid. We sell them in packs of twelve at the counter (example prices).