Searching for a cartoon series...

I remember when I was a kid in the very late 90s/very early 2000s, I would often watch the various saturday morning TV that was broadcast on terrestrial. Large shows like SMTV Live and Live & Kicking, which would show cartoons inbetween various sketches and cartoons and games.

I remember that on one of these, I would watch a cartoon or anime (I had no idea what an anime was back then; but what I recall it seemed to be vaguely anime-ish), which I now would love to find the name of. Unfortunately I have no idea what channel or show it was on - though must have been either BBC1, BBC2, or ITV, and all I know is that it was broadcast at some point between 1999 and 2003.

The drawing style was pretty good, it looked kinda like Americanized anime (sorta like Avatar: The Last Airbender). Definately not CGI. Some sort of cell-shading I think, with lots of light pastel colours and clean lines.

As for the plot of this cartoon/anime...I can't remember much about it at all. It was set in a subtly futuristic city - monorails were present, and the cars were streamlined and vaguely futuristic; but it was nothing over the top.
Could have been set in the next 30 years or so. The city was on the coast, and it seemed to be either in Asia or North America. The characters were a bunch of teenagers (maybe...5 of them?), who would go on adventures and stuff. I recall that one of the kids, a girl, belonged to a very rich family. She lived off the coast on some sort of artificial island off the coast of the city, and their mansion had a large glass dome over the top.

I can't remember much about the other characters at all, except that there was a black family, and two of the kids (a five year old or so and a ten year old or so) would hang out with the rest of the gang.

As for plot points, the only story that is clear in my mind goes something like this. The black family's father was mysteriously going off in the nights, and the two kids wanted to know where. The whole gang of kids then one day followed the father along the monorails and through the city, and followed him to a nightclub, where they discovered he played a trumpet/other sort of brass instrument to make money on the side, to support his wife and sons. I think there might have been a scene where the bouncers threw him out for some reason, to the horror of the other kids who were watching in the shadows. Thats about all I can remember.

It isn't much to go on; but if someone could somehow work out the name of this cartoon/anime, I'd be very much oliged! I've been searching on and off for years. I’ve searched Wikipedia and IMDB a number of time; but since I can’t remember the title or any of the characters name’s, its somewhat impossible.

Thanks!