I can understand that hesitation, Sadurian, and Frumpkis, above, - but at the same time, that worry is mostly a reflex reaction usually based on a misconception. A properly proportioned halfling, with the body ratios of a mature adult, doesn't stand any chance of being taken for a human child, at all - at least not by anyone who actually looks - but this is something that a lot of people don't realise until they actually have a visual reference to compare and see - which, unfortunately, can be very hard to come by. I feel that many people feel an instinctual worry or discomfort at the idea that they might end up looking like nine- or ten-year-olds, or pre-teens (a legitimate thing to not want, of course), but the truth is very far from that, and that danger isn't really a risk, if it's done properly.

Here's some quick background statistics though, if it helps:

Your average adult halfling is about 3 feet tall.
Your average human child is about 3 feet tall when they are aged between 1 and 2 - it may genuinely surprise some to read that and think on it, but any older and they're already notably taller than a halfling ever gets.
In terms of body ratios, an average human child of that age and height presents large head-to-body proportions, and smaller limb-to-torso ratios as well, not unlike the halfling models we currently have in game.

A quick reference:


This is one of the more commonly used charts that illustrate, in rough abstract, human developmental proportions - they represent 1 year old, 2 years old, 6 years, 12 years, and adult, respectively.

Giving halflings the body proportions of a mature adult would actually make them less likely to register as a juvenile creature to our senses than the current models do; it is precisely the having of a larger head and smaller limb-to-torso ratios that makes them more likely to be interpreted as juvenile by us. This isn't so much allayed by anything in the current models, as it is the case that other elements of the current models override that instinct with a sense of something being 'off' or 'wrong' (The head to body ratio would make our senses trigger as juvenile, but for the way that the actual head structure and model are clearly adult in features, for example).