Hi, I've got a book on natural remedies for babies and children and there are some great concoctions in it for colds and runny noses!
Apparently a herb called "hyssop" is an ancient cure for respiratory problems and bronchitis; it is an expectorant. You can use it in essential oil form, very diluted, for a chest rub. Or you can use the dried form to make a tea.
Elderflowers are very safe and effective for colds and chesty coughs. It can also be used in a tea, even for babies. Chamomile is a soothing herb; licorice root is also soothing as well as an expectorant, plus most children like the taste! Thyme is an antiseptic, astringent with anti-fungal properties. Great for clearing congestion in a steam vaporiser/humidifier; use essential oil in an oil burner - you can also add tea tree, lemon, and/or lavender oils.
Add 2 drops of peppermint oil to baby's bathwater, mixing first in almond oil, for bubs with a stuffy nose. For children over 12 months, you can make a decongestant chestrub with 2 drops lemon tea-tree oil and 3 drops of tea-tree oil in a third of a cup of almond oil; or 2 drops juniper oil and 2 drops of lemon oil with a third of a cup of almond oil.
If anyone wants the recipes for the cough mixture or any of the teas, let me know - this is getting a bit long now! Hope this has been helpful or interesting!