Hey preeah! Sorry for taking forever, but I hope this review makes up for it! Since this was a requested review, I'm gonna be nitpicky for you, especially with your characters, beause you specified in your request for me to look at them, so I hope that's alright! I'll just jump right in:
After reading through the entire chapter, I think you have a very solid prologue that gives us a nice insight to Peter before Hogwarts. You seem to have a really strong grasp on who your version of Peter is, even though this chapter focus' more on the Grunnion's than it does on the Pettigrew's, I feel confident that you know who your Peter and Deora are - both as individuals and as a friendly duo. It's perfect that you've instilled that in your readers already from this short introduction alone!
However, the Grunnion family as a whole is not coming across quite as strong. In fact, they seem to be written just a bit too perfectly, almost like a Stepford family, with their picture-perfect home life and this cookie-cutter image. Do you know what I mean? I'll try to explain: When I was reading, I honestly had the vision in my head of mom in a summer dress, the very image of a Stepford wife, Dad in a sweater vest with a side part in his hair who's only ever stern with the kids, never angry, and then takes them out for ice-cream, and the kids only ever pick on each other, but never truly fight because they're just that close of a family. Very 'Better Homes and Gardens' magazine-like. Of course, one could argue that this simply is how it looks from Peter's perspective, considering his home-life is the direct opposite, but it just feels a little too perfect over there. That's 100% just my opinion, though!
I think a big contributing factor as to why I feel this way about the family is because of the kids. I really feel that they are acting just too young for their given ages - especially Deora. With the dialogue, the 'mama', the 'daddy', the hand-holding with pops - I honestly would have pegged Deora around 6. The thing about 10 year olds is that they're just now starting to search for some independence. I'm not saying she can't still find herself attached to her parents/family, but she's just coming across very, very young.
So, I think the Grunnion's being related to the inventor of dungbombs is funny and original and I like that you had some fun with that, but I have to ask: After the boys put the dungbombs in Deora's shower (does she really have her own private shower? Or does it just read that way? Are they super rich so that each kid can have their own personal bathroom, or was that detail simply overlooked?) and she comes downstairs smelling like poo, did she ever go back up and clean herself off before going out? *rereads* Nope, LOL, that's pretty gross - you may want to adjust that. :-p
So after the theater, when exactly did Peter come out from hiding behind Deora's parents to being in reaching distance of his dad, who drags him away? I think you missed that step.
Here's a few small mix-ups:
"Peter was almost positive she has (had, not 'has') been as well." - Since this chapter is being told in present tense, make sure you remain consistent or it really stands out!
"She'll (She'd, not 'She'll') never admit it, but she was terrified of going(.) and (no 'and') (However,) with Peter around, she'd feel a bit more at ease." - You switched to present tense again, but also this sentence doesn't read very smooth without those additions. There's other ways of fixing that sentence up, too - that was just the first one I thought of, is all.
""You and your Mudblood wife are careless and..." - Since he's being cut off instead of simply trailing off, it should be a '-', not '...'. Also, you forgot your closing quotation mark!
Something I noticed with your writing is that you tend to repeat a lot of things (words, the meaning of a phrase) quite often, so I made a list of the ones I caught:
Did you know that you say the phrase 'blue eyes' three times in first four paragraphs? I'd consider mixing that up, a bit.
"Mrs. Grunnion asked curiously, confusion evident on her face." - Those two thoughts are rather redundant: 'curiously' and 'confused' about the same thing. We don't really need the second half, as it doesn't provide us with information we don't already assume from the first half.
"...they began to discuss Hogwarts since Deora and Peter would both be attending Hogwarts next year." - Repetative with 'Hogwarts' - I'd consider a replacement word, even as simple as 'school'.
"They both knew this would happen(,) even though, (no ,) they both wished it wouldnt." - Repetative with 'both'.
"I did no such thing! Don't come to my house and accuse me of such atrocious things!" - Repetative with 'thing(s)'
This line at the end: "He was dead serious." sounds redundant following the line before it. This is the same situation as the 'curious'/'confusion' thing I talked about earlier, where that sentence doesn't provide us with any new information - it's essentially the same line that precede's it, just phrased differently. Sort of like empty words.
Alright, so like I said, I was very nitpicky, but please don't get me wrong! This is a fine start (I mean, seriously - look at your huge fan base already!), but I read through almost every review for this chapter before writing this, and most the compliments have already been repeated over and over, so I wanted to supply you with a different perspective, not another of the same old review, haha. But I'm excited to see where the story is heading! You have me intrigued, especially with the author's note that we'll be switching to first person Deora!
I hope this review was helpful! Keep up the great work, preeah, and I'll see you in chapter two! :-D