8 is a big birthday--it's when a kid can be baptized into the Mormon church. It's called the age of accountability because it's thought they are old enough to choose to follow Christ, get baptized, and take responsibility for their choices thereafter. ETA before this they are called a "child of record"--which means they're on the Sunday School attendance rolls and listed as part of your family, but not official members of the church.
I never lived in the Morridor, but in my experience you'd have a normal birthday party, and on a separate (but close) date, have a baptism and invite family and friends for the baptism and typically a luncheon afterwards. Your family often gets to participate in the baptism--performing musical numbers, saying special things about you, giving prayers, giving short messages about what a special day and why, etc.