One of the best things I ever did was to follow the advice of my pediatric nurse practitioner friend who encourages us new mom's to regularly spray salt water into the nostrils of our babes. My nearly 4 year old now goes and gets the refillable squeeze bottle and brings it to me when she is even a bit stuffy as she knows it will make her breathe better. In some seasons we will do this up to 4 x day. It's as natural as showering your outer body. Big people do well with nasal douching (check into neti pots) as well.
The great advantage to all with this is that any bacteria or excess mucous that is still hanging out in the sinuses will be flushed out thereby eliminating the need for the body to metabolize it out.
The key is to start as early as you can so that they become accustomed to the experience...make big fun of it and be sure to have the experience how free their breathing is after it is done..."now doesn't that feel better?!"
Usually I'll lay my daughter across my lap (face up) and ask her "which side first?" She'll then point to it and I quickly point and squeeze trying to get as much up into the sinuses as possible...sometimes we'll repeat it. I'll sit her up pretty immediately while she tastes "the salty" and I'll either encourage her to blow then or do the second side and then blow.
The salt solution ( about 1 teaspoon to 8 oz ) will continue to draw from the sinuses excess fluid so you may be getting some pretty satisfying blows for about 1/2 hour.
K. Gilliam, LAc.
Rolfer/Feldenkrais practioner