please help identify a mystery tree

Can you post a photo of it?

Agree with Milky we can't possibly i.d. without a pix. You've posted one pix. of shrub which might, or might not, be a laurel... pix of the tree/shrub you are asking about please

Evergreen with berries - possibly Yew but I am being very presumptive without a better description and a picture.
Regardless, if you don't know that it is safe then you should assume that it might be toxic and should teach the toddlers to leave it alone.

OK, not Yew. I don't know what it is but the berries are not something that the children should be eating so they should be kept away from it.

I have looked at the plant you posted and can confirm that it is an Elaeagnus. The fruit are very astringent but not poisonous.

Assuming that the one and only pix you've posted is of the shrub then do not let your children eat the berries! By now you may be in A & E dealing with them being stomach pumped...

For god's sake all of you unless you know what a berry bearing shrub/tree is do not eat and more specifically do not allow your children to eat!

I looked on a site I have as a 'favourite' and Eleagnus doesn't appear on the poisonous list.

However, your children have to learn NOT to eat anything without your permission, as Moongrower says.

Moon grower is of course quite correct in that if you do not know what the shrub is, don't eat the fruit. The shrub picture you have posted is definitely an Elaeagnus and their fruits are not toxic though I still wouldn't eat them. The shrub in question is this one in Dcj's photo's as Dcj pm'd me with it.

This makes interesting reading, all of the species of Elaeagnus listed here have edible fruits though I must reiterate, don't eat them just in case.

And I'd just add that its really important to teach your toddlers to not eat anything growing in the garden - I once let mine pick blackberries out there, not realising there was a woody nightshade plant further back - my 2 year old son found it, ate a berry off it and ended up in hospital for 2 days, so even if you teach them some things are fine and some aren't it's still dodgy. When they're older, you can get them to learn which is safe and which isn't. More than half the plants we commonly grow in our gardens are toxic if eaten.