Being a stay at home mom, home-schooling one of your children, and doing the daycare thing at church can in no way be done by a selfish person. Also, would it be selfish for you to go fill up the gas tank in your car before you go grocery shopping? No, gas is totally necessary to run a car. In the same way, you need to fill your spiritual gas tank by taking time out for yourself, so that you can have the mental energy to minister to your children.
Here is a quote from one of my favorite Christian authors that may encourage you:The mother's work often seems to her an unimportant service. It is a work that is rarely appreciated. Others know little of her many cares and burdens. Her days are occupied with a round of little duties, all calling for patient effort, for self-control, for tact, wisdom, and self-sacrificing love; yet she cannot boast of what she has done as any great achievement. She has only kept things in the home running smoothly. Often weary and perplexed, she has tried to speak kindly to the children, to keep them busy and happy, and to guide their little feet in the right path. She feels that she has accomplished nothing. But it is not so. Heavenly angels watch the careworn mother, noting the burdens she carries day by day. Her name may not have been heard in the world, but it is written in the Lamb's book of life.
May God bless you in your unselfish ministry to your children