I agree with VILLETTE
The way I would do it is sit them down and explain you are sorry , but you were letting a friend store it their to surprise their kids for Christmas. the go on and explain to them you know how much they want one but you really can't afford it this year and maybe they all could make a plan how for next year they could get one if they all followed a plan.
of course if you already told them it was for them.... LOL.. this is all useless and I say MAKE THEM WAIT

If you give it to them now you will feel obligated to get them MORE for CHRISTMAS