Five kids? Wow S. - you are way outnumbered! But you also have so many helpers for this particular task :o)
Why not have the older kids help with the potty training - a boy for the boy and a girl for the girl? The youngest in the family are always impressed and want to follow the advice/actions of older siblings.
Have your oldest boy take the boy into the bathroom with him when he pees. Have your oldest girl do the same with the girl. This process of "do as I do" will be very effective. Let them ask the little ones to come along: "Come on Susie - it's time for us to go to the bathroom!"
Keep the potty chair on the floor in the bathroom for these "lessons".
Now that summer is here, the perfect time has arrived for this process to easily unfold before August. The more the little ones see using the potty as the way things work, the more likely they will be to identify the bathroom and the potty as a part of their world.