My kids are grown so I have not had to do that calculation - but my understanding is it is the same as your household expenses... so if you bought the toys for your kids only 100 percent of the cost would be yours regardless of if they only used them 2-4 hours a week for personal use .... but because your are sharing with your busIness you can write off that portion the rest of thectime you are not open gardless of your kids actual use is "personal use" ... does that make sense?