Effective use of modals
Title of text- simple, hand-drawn style and direct appeal for help (to two audiences - childline and ideal reader) works effectively to establish a voice and identity for the rest of the ad.
The use of one clause is straightforward and the use of modal auxiliary ("...can you help me?") adds a simple appeal on the part of the narrator.
If this had been switched modal (will or could, perhaps) the effect might've been less powerful.
Contrasting register
The first text box in the main part of the ad uses a very different style from much of the rest of the text. Here the noun phrases "an integral part of the NSPCC" and "a free and confidential service" sound more formal and seem to come from a different register (that of social work and care) than the style used in Molly's own account.
It's perhaps this contrast in registers that shows how the NSPCC can offer expertise and experience to help Molly and children like her, framing her lonely and desperate experience with the language of care and support.
Manipulating tense
The use of present tense here (shown by "am" and its the contracted form of "m") helps establish the narrative and the voice of the narrator. There is a switch into the simple past tense in the second sentence with the verbs "called" and "was" before the scene is completed using the past perfective "and my Mum still hadn't come home"
Revealing insecurities through grammar
The insecure status of Molly is highlighted by two verb processes in this section. In the first sentence, the subject of the clause ("she" i.e her mum) keeps leaving the children alone, so they are the object of the verb phrase "kept leaving". In the second sentence, Molly herself is the subject ("I") but in a passive construction where she is receiving the action of the verb "to be allowed" ("wasn't allowed).
This means that the mother is shown to be responsible for the process of leaving the children alone, while Molly is the victim of the process of not being allowed to answer the door; this contributes to the representation of Molly as lacking control and power in her life.
This is then accentuated by the lack of knowledge she has in the clause "I didn't know how to take care of him". The child-like compound sentence structure of the final sentence and the choice of the adverb intensifier "all sweaty" add to the presentation of Molly as lacking in experience and confidence: hardly surprising, given that she's only 10 and shouldn't have to deal with situations like this.
Adjectival choices and noun phrases
The simplicity of the adjective choices here again reflect the age of the narrator ("lonely", "scared" and "nice") and the straightforward reassurance that Childline offer her, but once again the lack of control Molly has over her own life is reflected in the last compound-complex sentence which all hinges upon the final clause ("...when I heard Mum's key in the lock"). Even at this stage of the narrative, the choice of the noun phrase "Mum's Key" rather than "Mum" highlights the absence of the mother in her children's lives.
Language choices for an upbeat ending
The last part of Molly's narrative returns (in part, at least) to the present tense she began with ("Tommy and me have visits with Mum now") and there is a move away from Molly being at the mercy of verb processes to a degree of control: she and Tommy are the agents of the verb "to have". There's a nod to the future with the use of the modal auxiliary "I will never forget..." so a suggestion that she doesn't have to concern herself all the time with what is happening now but can think ahead once again. The final complex sentence "that makes me more confident whenever I get nervous" foregrounds the positive main clause with its comparative adjective phrase "more confident", rather than the nervousness described in the subordinate clause ("whenever I get nervous"), creating a more hopeful impression to finish with.
Like many other choices of language and structure, think about how this might have been different had the text producers chosen a different structure. Here it works well because it fits the overall pattern - ending Molly's story with a more upbeat tone.
The creation of hope
The overall picture from this charity ad is one of hope and its clear to see that this is created in a number of ways. There are lexical choices which make a difference - so individual words and their meanings have quite an impact on how we read the text - but grammatical choices, often to do with tense and aspect (how time is represented through language) and clause linking (how clauses are linked and the relationship between them) and have a big impact. Beyond the level of words and sentences, there's also the use of a wider structure, not just in Molly's narrative but in the whole of the ad itself.