Patio basin fish tank. Tips and tricks?

There is space on our patio for a 60x40cm basin fish tank. Our grandson is at the stage of loving fish so it would be good to install one. It wouldn't be in direct sunlight at any time of the day. There is a socket above the area to add a pump. There are 2 neighbor's cats that come around, which is okay as it means we've never seen a rodent here. 

Will any plastic tub do, or does it need to be one specially made to hold fish?

How high should the top be elevated to stop the cats from going fishing? There are no wall structures for them to stand on next to it.

How deep should it be?

Should gravel be placed at the bottom?

What plants should be put into it?

What fish should be put into it? We don't want a lot. Perhaps half a dozen. 

The grandson would like little shrimp. Could they live and thrive in such a habitat?

What size pump should be put into it? Turned on for 6 hours per day would be enough?

How long to let it settle before putting fish and shrimp into it? 1 week?

Would there likely be algae bloom after putting fish into it?

Feeding once in the morning once in the evening? 

What about water changing? Just top it up with the garden hose as it evaporates? Or take out a few bucket loads every week and replace with garden hose water?

TIA.