We do a mixture of things - we obviously have the times when we are all of as a family - at other times we days of seperately to cover, I buy extra holidays to cover extra days and we also use an out of school care provider for the rest. As regards a childminder, you will have the same problem as we do in that you don't need care during term time, you only need holidays. Childminders will have the children they have regularly either all day or those they take after school during the holidays, they may also have their own children all day as well so they are rarely ever able to offer spaces for other children for holidays only. Other options could be: finding an employer who is able to offer term time only working, having your child spend a week of the holidays staying with a relative if you have no-one near by, often sports centres run football, tennis or rugby clubs during the holidays. Share care with another childs parents (you could consolodate your hours during holidays maybe so that you work 3 long days instead of 5 short or something) I have never yet failed to find something suitable for them to do over the last 5 years.
I agree though that you cant really let something that far away influence whether you have children or not. These things have a way of working out. I will be in a new situation soon where my boys will be too old for out of school care when they hit high school age (they are 10 and 9 now) but they will not be responsible enough to leave at home either! One at a time maybe, but not two together. So the hunt for me will start again soon.