My daughter had to get over the struggle hurdle in order to enjoy reading. Are they reading at grade level or are they below? Their teacher(s) ought to have tested them this year so that you know.
The only way to improve reading is by reading. I say make the rule read 20 minutes per day, though not necessarily in one session. That has been the daily homework for my daughter, and her summer bridge books recommend that , too. (I hope your children's teacher had made 20 minutes of reading a day their homework. If not, yes, make it a house rule).
Playing imaginary games is a perfect post-reading activity. Be sly and set out costumes and toys that can be used as props for play acting scenes from the story you are reading. If the story has characters selling lemonade, have a lemonade stand. Careful what you read to them! If they do not naturally see the connections between play and reading, then organize this type of play yourself to show them how to do that. Make puppets and put on a show of the book. Act out a scene. Make a book about the story, with different scenes on different pages. Doing the story is a great companion to reading the story. This helps them visualize the images. It also helps all types of learners to access reading.
Imaginary play, building things, getting exercise, reading, doing some household tasks can take up the bulk of a day. Limit the electronic device time. Don't let the devices take away from reading time.
Kids do like to be on the go. There's no rule (at home, anyway) that they have to be seated while you read aloud to them. Sometimes my daughter plays or draws simultaneously while I read aloud to her. She is processing what I am reading to her. Understanding what is said is important too, along with decoding the words on the page. Reading aloud also builds up vocabulary, works on reading stamina, and helps kids know what reading should sound like. I've also seen articles about kids sitting on those big yoga or exercise balls while doing seat work. This allows them to move while they read or write or do math.
My DD and I are currently buying the Nancy Drew Notebooks series and reading those. This is not the original, which has teens driving around, but eight-year-old girls solving mysteries kids can relate to. The books also show what active eight-year-olds can do with their time through the stories. The series is not available new at bookstores, so you'll have to go to the library or find used copies online at Amazon or eBay. And a word of caution: Not all the Nancy Drew book series are appropriate for eight-year-olds. Some are updated teens with dating and murders. The Notebooks series is the place to start. But there are a lot of books out there. Keep trying different genres.
I spent six months being anxious whether DD would get over the struggle hurdle, but she did. Best wishes.