Garden plans!

[tellezara]

Hi guys! I found this comm via dw_news and hope you might be able to advise me.

We moved house last October. The back garden is enclosed and doesn't get a huge amount of sun. It is mostly paved with some raised beds, so we've planted some shade loving greenery. In the centre is a very sad token patch of lawn (with bald patches) measuring about 2 x 1.5m. We want to dig this out and turn it into a Zen garden - I was going to put down weed mat with sleepers on the sides and fill with white gravel. But now my husband quite likes the idea of having a small tree in the centre of this. I'm a bit iffy about this due to the small space but I don't know enough about gardening to have a proper justification for my unease.

1) Are there any good tree types for a shaded garden, that don't grow large but don't require the daily upkeep of bonsai?

2) Is 2x1.5m enough space for tree roots without them going under and distorting the paving if I plant the tree in the ground??

3) How can I have a tree but still keep the weed mat down?

Thanks for any advice you can give!