Please don't worry about a protruding belly. It's perfectly normal well into the preschool years
My daughter isn't overweight either but has always had a belly and thicker legs and needs a bigger waist than length, so we wear nothing but leggings. The few times she's worn jeans (once for an all-cousin's picture) they came off as quickly as possible because they were just too snug. If you have to have jeans for something, I think cropped/capri is the way to go, if not, Target has really inexpensive leggings that hold up well.
Susan
Mommy to a 97th percentile Guatemalan girl, who at 3 1/2 is wearing size 6.