I don't have an extremely realistic artstyle, so I fear that whenever I try to draw my very short character, they'll just look like a toddler in comparison to the others. What can I do to prevent this?
It all comes down to proportions. When drawing humans, the proportions of different body parts are usually measured in "heads". One example by Leharc--BlueHeart on DeviantArt: (click the image to magnify)
An infant is usually 4 heads tall, an adult 7 - 8 heads. In addition to that, the head of an infant has an almost circular shape, while the head of an adult is more oval.
- the "M old" figure and the "10 yr" one are both 7 heads tall, but the "old" one is taller because their head is oval.
- The hand of the "3 yr" figure aligns with the hip bones. The hand of the "adult" figure only starts at the hip bones. The finger tips reach halfway between hips and knee.
- The torsos of "adult" figures tend to be 1/2 - 1 head shorter than their legs. The torsos of children are longer or as long as their legs.
- The necks of young children are almost invisible. The necks of adults are clearly distinguishable from the shoulders and the head.
- The arms and hands of young children tend to be very wide and have the same circumference throughout. The arms of adults have different angles and circumferences at the shoulders, biceps, elbow and wrist.
- The entire hand from wrist to fingertip is usually one head long. That means that children have shorter hands than adults.
- The heads of children are as wide as their torsos. The heads of adults are narrower than their torsos / rib cages.
Let's transfer these proportions to some fantasy races of different sizes. The following example is made by Clyde Rohrer.
- The dwarf, halfling and half-orc are examples of stocky builds. Their torsos and legs have the same length and their fingertips reach halfway between hips and knees.
- The gnome isn't too far off, but her legs are longer than the torso. What distinguished her from a child are her secondary sex characteristics (breasts and wide hips).
- The elf, human and half-elf have very female bodies because their legs are approx. 1 head longer than their torsos. You only see that the elf is male nonetheless because of his secondary sex characteristics (square jaw, flat chest, muscled upper body).
I guess the halfling and gnome are the most at risk of being confused for children. For the gnome the distinction is clearly made by the secondary sex characteristics. The halfling looks adult because he has a square jaw and shoulders (in comparison to the very round lines of an infant), a skull that's narrower than his torso, a clearly defined neck, long arms with varied width and a muscled chest.
If you don't want your character to be muscled, you can go for the androgynous look and make the legs and arms longer than the torso. Try to keep the head narrower than the chest area, even if the face isn't human. You can also add some angles in the face and shoulders to make them look male.
I hope I didn't butcher your character too bad, but I tried to make them look more adult. The shoulders are less round, they now have a neck, the face is narrower than it was and has more angles.