I have a 9 (10 at christmas) year old dd. She is getting some games for her 2ds - i recommend them if they don't have one. Or if you have a higher budget the Nintendo switch is great as a portable console or multiplayer on screen. Super smash bros is coming out this year which looks amazing (dh has a switch and plays with my dds) she also likes playing legend of Zelda, dragonball and Mario kart.
Are they into any particular fandom? If so could get merchandise relating to that. Lots if gaming, different tv show/film t-shirts, books, figures around. QWERTEE, emp, truffle shuffle, game, Amazon and eBay are all good places to start looking.
Would they like a subscription box like Japanese sweets, loot crate, geek box. Or subscription dd1 loved her beano subscription- we wrapped the annual then a note. Nice gift that keeps going.
Movie hamper- popcorn box, popcorn maker, new film, favourite sweets/chocolates and soft drink. Could also wrap a fleece blanket - Primark/asda/Matalan are great quality and v reasonable.
New backpacks/pencil case. Maybe more expensive than a basic one you would buy. Hype is popular amongst dds friends (boys and girls).
Graphic novels- dd likes adventure time, the Simpsons, phonix comics. I've also bought her a how to draw comics book this year.
Sharpies and adult colouring books - she has Harry potter, animal and Pokemon ones.
I'm looking at the Lego movie maker to go with her tablet. It's around £12 on Amazon, will give her something to do other than roblox and watching slime videos.
Books - there's a new wimpy kid,dork diaries, captain underpants, Dogman which she loves so I've pre ordered those. She also enjoys her kindle which could be an option for your boys if they like reading (not the fire but an actual kindle. She has a fire tablet too) or the book people do great sets of books for reasons prices.