Towards the beginning, Lacey Chabert's character states in the voiceover that her husband had been sick for two years. On Christmas Eve, the mother-in-law states that she took care of her son for three years.
The double rainbow seen at the lake is not how a real double rainbow looks. The image shown is just one rainbow imposed above another rainbow, with both having the same order of colors. In a true double rainbow, the bottom rainbow will have red at the top and blue at the bottom, the second rainbow will have the color orders reversed, as the second rainbow is a reflection of the first rainbow.
Approximately ten minutes before the end of the film, Michael's mother and his daughter Charlotte are cooking dinner. The mother has oven-cooked a turkey in a covered roasting pan. With oven mitts, she removes the covered oval roaster from the oven and places it on the stovetop, carefully removing the lid. The young daughter Charlotte then bastes the turkey, but while doing so, casually rests her left hand on the "supposedly" piping hot rim of the roasting pan.