Shapechanger. The mimic child can use its action to polymorph into an object or back into its true, amorphous form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies. Maintaining it's new state requires concentration (as if concentrating on a spell). If the mimic child loses it's concentration, it can't shapeshift for a minute.

Adhesive Grab (Object Form Only). The mimic child adheres to anything that touches it. A small or smaller creature adhered to the mimic is also grappled by it (escape DC 8). A mimic child can also try to adhere to a large or larger creature. The larger creature must make a DC 10 strength saving throw on each of its turns, or have it's movement halved for that turn while the mimic is attached. 

False Appearance (Object Form Only). While the mimic child remains motionless, it is indistinguishable from an ordinary object, unless a creature suceeds on a DC 15 Perception (Wisdom) check, or has a passive perception score of 16 or higher. The DC for the check lowers to 10 if the mimic child is frightened, and the passive perception lowers to 11 if the mimic child is frightened.

Grappler. The mimic has advantage on attack rolls against any creature grappled by it.

Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 1) piercing damage plus 4 (1d4) acid damage.

Ram. Melee Weapon Attack:  +3 to hit, reach 5ft., one target. Hit: 5 (1d10) bludgeoning damage. If the mimic child is in object form, the target is subjected to its Adhesive Grab trait. The mimic child must move 10 feet in a straight line before using this attack.