This has the potential to be a wonderful essay! After analyzing all of the deception found within both novels, I think the best option for a cohesive thesis would be this:
The characters of both Huck and Annie continually use deception and lies in order to continue antagonism with and encourage distance between a parental figure.
With regard to the character of Huckleberry Finn, this antagonism is best shown by his thoughts and actions toward his father. Huck is disgusted that his dad would attempt to cheat him out of his monetary inheritance that he has secured from the judge. Despite a long-standing hatred for his dad, Huck finds this quest for money just furthers his negative feelings towards him. Add to that antagonism Pap's physical abuse of his son both through beatings and starvation. This prompts Huck to decide this at another point in the novel:
Human beings can be awful cruel to one another.
It is both aspects of antagonism here that lead to Huck's deception: namely, he fakes his own death. Specifically, he kills a pig and drags the bloody carcass in order to leave a trail of blood to the river. Once at the river, Huck uses a canoe to escape to Jackson's Island to watch what happens. Sure enough, cannon fire announces Huck's death. Huck is now a master of deception as a result of antagonism!
Similarly, the character of Annie in Annie John is also guilty of deception through antagonism with a parent. Again, the mother begins the antagonism by insisting her daughter dress in a similar way to emulate a simple housewife. When Annie wants to hang out with "The Red Girl," she continually lies to her mom about where she is because her mom doesn't want her to play marbles. No matter what Annie says, even if it is the truth, her mother accuses her of lies and deception. Here is a perfect example of those feelings of antagonism:
Out of the corner of one eye, I could see my mother. Out of the corner of the other eye, I could see her shadow on the wall, cast there by the lamp-light. It was a big and solid shadow, and it looked so much like my mother that I became frightened. For I could not be sure whether for the rest of my life I would be able to tell when it was really my mother and when it was really her shadow standing between me and the rest of the world.
Even though this is not quite as serious as the faking of Huck's death, these lies do separate mother and daughter so much that Annie happily waves goodbye to her mom from the boat as she goes off to study elsewhere during her adult life.
Hopefully these ideas as well as these primary source quotes will help you begin your essay.