OK, so the kiddos took a seed from an apple tree and planted it in our front yard. Ha ha, how cute.
They are now convinced a baby apple tree is growing in our yard. They have put sticks around it and I avoided it when I mowed the lawn.
Southeast Michigan, United States, by the way.
Nm. I decided I can’t be sure.
Did you think “no” because of the leaf shape? I can’t tell and wonder if apple leaves look like that when it’s a baby.
Some have sharp ridges, but not all. In your pic I see 2 kind of leaves, that’s what makes me unsure.
Maybe! Google “seedling apple tree” images.
But apples do not ‘come true’ from seedlings, they are all grafted. Even if your kids were patient enough to wait five to ten years for it to bear fruit, the chances of the apples being any good are very very slim.
It could have pretty flowers though 
FWIW There’s a volunteer - self seeded - apple tree on a bank by my house. The fruit is sweet and quite decent, not what you would call a commercial crop but I’ve eaten more than one.
My parents told me the same thing when I insisted on planting a grapefruit seed. It bore large, delicious grapefruits. I agree you’re probably right, but they might get decent fruit out of it.
There is a very high chance that the resulting apples will be ugly. Commercial growers don’t like ugly apples, and so they almost always graft. But there’s a decent chance that they’ll taste good anyway.
But, if it comes up crab-apples, you’ve got apple pie or cider 
They are, of course, grafted so that they have a strong, vigorous, disease resistant root stock. The seeds may also not breed true to the fruit, but I think they’d be grafted anyway. (IANAO).
Most likely they will be bitter, every McIntosh apple sold is a graft of a graft from the tree John McIntosh discovered in 1811. If you had a McIntosh apple tree, you would need a different apple variety, like a Golden Delicious apple tree, to pollinate it. They will not self pollinate with the same variety are the same genetic material.
The hard part is that because people don’t grow apples from seeds there isn’t a lot of information on what the saplings look like, but it does look like what I use to dig up below our crabapple tree growing up.
Have your kids watch this vlogbrothers video about apples.
Grafting is done to ensure consistency in the fruit. Just like siblings are not exactly the same even if they have the same parents, trees born from seeds will not be exact copies of the parent tree and there will be variation in the fruit. Taking as cutting from a branch and grafting it onto an established root makes an exact copy of the tree the branch came from, you could really say it’s the same tree.
You can also graft multiple trees onto one stump. My grandparents even had a single tree that bore both apples and pears.
The others are right about apples not coming true from seed, however, feral seedling apples are often far from completely worthless - typically they’ll be smaller and more sour than the parent, but will bear some sort of resemblance to it.
There are a lot of assorted feral apple trees in the hedgerows and woods near where I live - I’ve picked them and made cider, apple pies and preserves from them before - here’s a little exploration of some of them, that I posted on my website a few years back:
My friend at work says the pinkish hue and razor/pointy leaves indicate this is just a weed.
Is he right?
Or it could be THE weed. Check your local laws. 
[really rather obvious]
That’s not the weed.
[/really rather obvious]
Wait until you taste the fruit to decide if it is a weed, but it looks similar to other apple seedlings.
Not to someone who’s never seen the stuff in it’s wild state.