I have 3 children, 2 in-law children and 3 grandchildren all living very close by and even the grown-up children want attention! It's not a great idea to have them all present at once, as there can be competition for attention. When my children were younger, I tried to give them all some special time during the day for themselves. If their dad was able to take a couple at a time, that allowed me to give special time to one. Even homework time can be special because you are paying attention to what they are doing and it is a good opportunity to give praise and find out what they have been doing. It is possible, where you have a good number of years between the children to pay attention in different ways to an older one and a younger one at the same time. If the older one is no longer interested in sitting on your knee for a cuddle, then a younger one can be there getting a physical bit of attention, while an older one is maybe explaining a piece of work or getting a story read.
I try to share myself out between them all, to give even a small piece of individual attention to each one. This appears to work better than trying to give attention to all in a group at once.