The 14th annual party, organised by charity fundraiser Les Hoey, was held at Fir Park, Motherwell, on Sunday.
Children were given gifts and entertained by celebrity guests, including SPFL footballers.
But Mr Hoey and his volunteers were left "distraught" after a bag containing £300 in pound coins, which were collected as part of a raffle, was stolen. Two mobile phones and a set of keys belonging to a volunteer helper were also taken. Mr Hoey, from Wishaw, said: "That £300 would have gone towards buying Beyonce tickets for kids.
"Nothing like this has ever happened in the 14 years I have been organising these."