Mountain Biking - MTB newbie - advice on cost effective upgrades

I'm a novice when it comes to mountain bikes - spent most of my cycling years on road bikes - primarily vintage. I just bought a Performance M309 for my 10 yo son today for $40. I don't know much about these bikes or who Performance had make the frames other than it was made in Taiwan. Following their model numbers this would be a 1999 model but I couldn't find any specs on Bikepedia.

The bike has an aluminum frame that appears to weigh between 24-25 lbs - I was surprised by how light it feels. Other components (I suspect it's not all original)

Shimano Deore rear derailleur with 8 spd cassette
Shimano Acera front derailleur
Shimano shifters
Tektro brakes
Rock Shox Jett front suspension fork
Modus stem
Suntour MD300 triple crankset - 175 mm arms

It appears I need to true the wheels and put on new brake pads. The rear derailleur was acting up and tightening of the cables fixed that problem.

I've attached some photos and have some questions:

1) I have no experience with the style of brakes on the bike, although they seem to grab really well
2) I know Deore is a decent derailleur and I have some Tektro levers on a couple of vintage road bikes, but what about?
3) What about the rest of the components?

I don't want to spend a ton of money on it if I don't have to because my boys are notoriously hard on equipment. However, if there's something on the bike that I should realistically look at changing out now, what would that be.

Thanks ahead of time.

Great for $40. Looks solid too. Perfect starter bike your son if it fits, looks a little big for a 10 YO? Tune it up and ride...

25 lbs? Really? That seems super light for such a low-end bike. Have you weighed it?

Anyways, don't upgrade anything unless it breaks. That's my suggestion.

Anyways, don't upgrade anything unless it breaks. That's my suggestion.

I'm of that ^ opinion too. A non-semi-slick rear tire might be in order if the trails are soft or loose around there.

I've haven't got on the scale (the only way I have to get at least an idea of what my bikes weigh) with it yet but it is considerably lighter than the two steel MTB's I have. Both of those have alloy wheels. I was quite suprised by the weight because I was expecting a "beast" and it's not. Heck, I might even ride the thing.

My 10 yo is as tall as my 13 yo and has already ridden the bike. It seems to fit him although the saddle may need to come forward a little.

I have a couple of knobby tires that I'll put on it. We're on a heavy gravel driveway and I agree they will be a better, safer ride for him.

Thanks for the input.