Alfie and the Dinosaur
Once upon a time, there was a little boy called Alfie. He lived in a house with his Mummy, Nana and Granddad. One day, Alfie’s Mummy woke him up to show him something in the garden.
Nana and Granddad were standing at the back door waiting for Alfie to come and see. Alfie looked out of the back door to see a really big DINOSAUR standing there!!!!
The dinosaur was as big as the house. “Hello,” said the dinosaur.
“Hello, my names Alfie. What’s yours?" asked Alfie.
“My name's Jason,” said the dinosaur, “and I’m your new pet dinosaur!”
“WOW!!!!” said Alfie turning to his Mummy, “Can we go to the park and play Mummy?”
“Of course we can,” said Mummy, “We can take some sandwiches and have a picnic.”
“Can I have jam sandwiches please?” asked Jason, “They’re my favourite.”
“Of course you can Jason, I’ll make them for you.” said Nana.
At the park, Granddad and Alfie played hide and seek with Jason, then they played football. Nana and Mummy were watching them and cheering. After playing football, they were all tired, so they went to sit down and have their picnic.
Alfie and Jason loved the sandwiches that Mummy and Nana had made them. After they finished their picnic, they started to walk back home. Just as they got home, an ice cream van stopped at the front of the house, so Granddad bought everybody a big ice cream.
After the ice cream, Alfie was feeling very sleepy, because it was nearly his bedtime. Alfie gave Nana and Granddad a kiss and cuddle and said goodnight. Mummy picked him up to say goodnight to Jason. He gave Jason a really big cuddle and said goodnight.
Mummy carried Alfie upstairs, put him in his pyjamas and put him into bed. As soon as his head touched his pillow, Alfie fell asleep.
“Goodnight Alfie, sweet dreams,” said Mummy, “we’ll be having lots more fun tomorrow.”
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I don't know if a critique of grammar is what you were looking for but I went ahead and edited it anyways. On grammar, remember: if you start out in the past tense, maintain that tense. You switched to present tense a couple times, as you can see in the bold edits. Also, remember to put your apostrophe/punctuation at the end of a quoted sentence, once again see the bold edits. Lastly, remember the apostrophe in a contraction, name is should be name's.
On the content of the story, this made me grin and made me think how much my nieces would love a story about themselves. If I saw this on a shelf, I would buy this for my nephew. The story is very sweet and could make the Grinch smile. I hope this helps. Cheers.