True Daddy Dom/little girl dynamics are in no way related to child involvement.
child involvement is the attraction to children. This includes everything in regards to the person being a child--physically and mentally. Not just a "childlike" personality or behaviors but everything involved with a person being a child (physical and mental).
DDLG involves a "little girl" but that person is biologically over the age of 18. She is likely physically and mentally matured but has a childlike wonder about her or just simply enjoys childlike activities. It doesn't actually make her a child. She is physically and mentally still an adult woman even if she pretends she isn't sometimes.
If you're looking for someone UNDER 18 then, sure, maybe you are looking into child involvement since under 18 is typically considered a child in most countries.
If you're fantasizing about having physically intimate contact with a child then, yes, you very well may be a pedophile.
If you're looking for an adult woman who likes acting silly and, at times, downright childish then you're still looking for an ADULT.
If you're fantasizing about a woman (with developed breasts, hips, thighs, height, weight, or other features that you would attribute to being an adult female) playfully acting childlike then that isn't a form of child involvement.