Heat some mustard oil and add crushed garlic in it and u can massage baby's feet and hand with this, steam would be good, Ajwain potli heat some Ajwain seeds on tawa little bit for few seconds make potli and u can rub this on baby's chest and back.  Also check the temperature should be warm not hot. Bf ur baby that is the best way to get rid of cold and cough.

the safest is the ajwain potli and mustard oil with ajwain and garlic massage.. 

also you can buy Vicks vaporiser which is quite safe for babies and actually made for them

rub baby Vicks on chest feet and head when he is asleep

you can apply saffron on forehead