Although both adults and children can hike in sneakers (aka tennis shoes or athletic shoes, depending on where you live), you'll all find hiking more enjoyable in sturdier shoes or boots. Hiking boots offer several advantages over sneakers. They have sturdy, grippy soles that prevent you from slipping on slopes and provide excellent traction when it's wet or muddy. Outer coverings made of heavy-duty cloth (like Cordura®) and/or leather protect your feet against sharp sticks and rocks. Boots with waterproofing or Gore-tex® construction enables you to enjoy hiking even in wet weather.
We bought our oldest son Jamie his first pair of boots for hiking just before his second birthday and noticed a significant difference, even on our short hikes at the local nature center. When he wore sneakers, he'd slip and slide down even minor inclines. The boots gave him much firmer footing, which is important to a toddler who isn't all that stable to begin with! In addition, he loved having boots like Mom and Dad and wanted to wear them immediately.
His first pair of boots weren't really "hiking" boots, per se, just a pair of leather boots with good soles from a children's catalog. We soon found that his feet grew too fast at that age to spend much money on boots for him and realized the boots didn't have to be top quality, since he'd outgrow them long before they wore out. We often bought tiny hiking boots for $15 or $20 at discount stores like Wal-Mart or K-Mart. We've gotten plenty of use out of these, as his younger brother now has an array of hiking boots available in every size as he grows.
As Jamie has grown older and able to tackle longer hikes and more challenging terrain, we preferred to get higher quality, "real" hiking boots for him. Since we hike all the time and know he'll need new boots eventually, we usually keep an eye on our favorite outdoor gear websites (see resource list below) and purchase boots in the next size up when we see a good sale price.
Resources for Children's Hiking Boots
* Local discount stores, like Wal-Mart, K-Mart, and Target (Note that these stores typically carry hiking boots as a seasonal item in the fall and may not have them at other times of the year, so think ahead)
* Catalogs and Websites (check for overstocks and sales):
L.L. Bean - catalog (800-221-4221), stores, and on-line (www.llbean.com)
Campmor - catalog (800-CAMPMOR), store in New Jersey, and on-line (www.campmor.com) - excellent prices and always has many items on sale
REI - catalog (800-426-4840), stores nationwide, and on-line (www.rei.com)
Lands' End - catalog (800-356-4444) and on-line (www.landsend.com)