Can i give a 3 yr old cold and cough robitussin (guaifenesin) and motrin at the same time ( children's)?

Possibly, but...: First, there are "robitussin cough medicines" out there that already contain ibuprofen.Read the label on the particular one you have to make sure you are not doubling up on that ingredient. Robitussin (guaifenesin) is just a brand name - it doesn't clarify what the concoction contains. Second thing to consider is that most cough medicines don't help a 3 year old. Some of them actually make your child cough more.