Table of Contents: Masthead Sticky Because children are lighter than adults, buying a kid's mattress is a bit different. Mattresses for kids don't need to be expensive, but some can be safer and more comfortable. The Nest BKB is our top pick because of its support and ventilation. Choosing a kid's mattress is different from choosing one for an adult. Because children weigh less, they're less likely to suffer from aches and pains as a result of a mattress that's too firm or too soft, said Daniel Ganjian, MD, a pediatrician at Providence Saint John's Health Center in Santa Monica,