Can u take advil for headache and sudafed n zyrtec for allergys at the same time for a 11 yr old child

Both Advil and Zyrtec are for ages 12+ unless you get permission from your doctor.
Can all 3 be taken at once ordinarily - it depends on which Sudafed you are talking about.
Tylenol is the preferred medicine for pain over Advil. Advil is ibuprofin, and is better for inflammation.