Reddit reviews Polyhedral Dice Double Colors Table Game Dice for Dungeons and Dragons MTG RPG DND with Gold Pattern Pouches 42 Pieces

Link?

Edit: found it https://www.amazon.com/dp/B07G5FK1HH/ref=cm_sw_r_cp_api_qMxLBb45YDSNR

The starter kit has EVERYTHING you need, with minor exceptions. It comes with 4 (or 5 I think) pregenerated character sheets that are only the first page, not the second or third page. Now you can download full character sheets and print them off for free so that's not a big deal. The starter set books also don't (if I recall) offer any real information on how you create characters from scratch--the main problem I found was figuring out skill proficiencies and proficiency bonus, which is why we eventually bought the PHB (skill proficiencies come from your BACKGROUND and class; you can find all this info for free online if you look).

Other than that though, the starter set comes with an adventure module that can take you from level 1-5 and has all the important monster and magical item info etc. in the back. So if you fight goblins, goblins are in the back of the book--you don't need the monster manual, and the goblin stats are identical in both books.

As far as dice go, the set of dice it comes with is all the dice you need but you can quickly find situations where you might need 2 d20s, or 2 d6s, or whatever, and rather than have to roll one dice several times it can help to have at least 1 or 2 other sets. Ideally every player would have their own set of dice but it's not required. There are plenty of cheap sets on Amazon, they maybe aren't the highest quality but they're good enough. I bought this to run a game with just last week:
https://www.amazon.com/gp/product/B07G5FK1HH/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

And yes, playing in "bursts" is completely normal--it's how the game usually works. A lot of players talk about doing 4-5 hour long sessions but I've never been a fan. I start losing patience after a third hour unless we're REALLY on a roll with progress. The book is divided into 5 chapters or so and ideally each one might take you one or two sessions to roll through.

You can use pregens for everybody if you want to, it can work fine. Wizards has a bunch of extra pregens here if the ones that come with the set don't interest your players. Some of them might want to make their own characters, but they might be able to find a similar character from this list.
http://dnd.wizards.com/articles/features/character_sheets

The starter set retails for like $20 and you can get it on Amazon for like $15-17. It's a no brainer. Don't dive into the other books right away until you have something else--IMO I wouldn't until you're almost done with the starter set adventure. I also personally would pass on the DMG, it's not like earlier editions where it was particularly vital, it's got a LOT of optional rules in it and is mostly for DMs who are interested in creating their own homebrew worlds--but Wizards publishes tons of adventures that are more or less ready to go out of the box and you don't necessarily need it. (For example the DMG has all kinds of tables about how to randomly generate traps and stuff, but if you buy a book that already has dungeons in it, you don't need to generate any traps, the traps are already in the book.) Other people might disagree but IMO a DM can get by with a PHB, adventure module and monster manual just fine.

Lastly, be prepared to have somebody else help the kid. 7 is IMO a little young to have a complete grasp on all of the mechanics you might need to have in motion--just as an example an attack roll requires you to roll a d20, then add your proficiency bonus, then your strength or dex mod bonus (based on if it's ranged or melee). Now you can have an adult add all that up beforehand and tell them "when you attack, roll the d20 and then add 5 to it" and they'll be fine. Just be patient with them.