I always suggest buying the herbs as they are the best. Tea bags are full of toxins so if you can find cammomile loose it is better also.
I have a one cup tea maker and I put in 1 T. of herbs and make a cup of tea. The black and decker machine does all the work.
I suggest you make one big cup of tea and split it between the two children. If you see they improve after three days you can increase the dosage for the the 6 year old. I would wait until the one year old is a bit older to increase, except in case of illness. In that case I would suggest twice a day.
Mind you, I cannot give medical advice but only advice to a friend.
Put one cup of water in a pan and heat and add in 1 T. of cammomile flowers or olive leaf and bring to boil. Remove from the stove and cool for 20 minutes and then drink.
If I was on a desert Island and Allah granted me three wishes, I would wish for black seed,honey and a life raft. No just kidding. Olive leaf. Have a great day my friend.