This is often a topic that comes up between groups of parents and often you will find that peoples opinions can be quite different. A holiday for many people is something that they only get to do once every year or so and they simply could not imagine going without their children with them. For other people, they may be able to go on holiday a few times a year and see nothing wrong with having a holiday for them and then a family holiday separately.
There is no right and wrong answer to this and it has to be up to each family to decide. It may be that a trip you want to do would not be suitable for young children so you decide to leave them with family for a week and spend some quality time with your partner. It is important for parents to spend time together on their own as often you can easily forget to make time for each other and this is often when people drift apart. If your children are happy to stay with family for a few days or so then having two holidays can be very beneficial for everyone. This also means when you go on your family holiday you will be more inclined to tailor it to be mostly for the children as you will feel like you have already had a break.