is common among this age group and try to give plenty of oral fluids, add dietary fibre to diet and encourage the child to go toilet daily. These measures make stools soft and loose so that she will pass stool easily. Still its hard stool you can go for laxatives like lactulose
after consulting your Pediatritian. And for mucus in urine go for complete urine examination to rule out any urinary infection after seeking the advice of your doctor.