Is Colton Burpo's Heaven For Real?

The "Heaven Is For Real" book describes heaven as filled with little kids. But the book of Hebrews describes the saints in heaven as "the spirits of just men (i.e. people) made perfect." Why would God freeze the appearance of a deceased person at the point of, say, eight years old? If you are a Christian who dies at 87 years old, do you look 87 years old in Colton Burpo's heaven? Hebrews 12:23 implies that believers are perfected in heaven, not in a state of non-maturity.