DIY 2-Way Bluetooth Speaker with Sub for a Tuk Tuk (Rickshaw)

So this week I took delivery of a lovely Bajaj RE4 Tuk Tuk, https://a2zvehicle.com/bajaj-auto-rickshaw-price-list/ and I'd like to add a stereo to it. My first thought is to buy a cheap bluetooth amp like this one:
ebay and hook it up to some speakers.

Now it just so happens I have a pair of Mackie CR3s, Mackies which have a faulty amp, so I was wondering if it is possible to repurpose them some how. Maybe build a box for the rear parcel shelf and fit them into that. I also have an old Eltax sub speaker driver, like this one Sub

So for a bit of fun if I could add that to deal with the bottom end that might be cool.

I'm wondering if that little amp will be capable of running the Mackie 2 ways mids and tweeters, and at the same time the eltax sub.

What I have no idea about is creating the crossovers, and also how I can run the single sub from the stereo feed of the amp. Presumably I need to split the signal somewhere?

I'm not looking for sonic fidelity here, it just needs to be something cheap and cheerful which can put out a little bit of bass!
 
Thanks for the reply, it doesn't have a trunk/boot but it does have a big parcel shelf area behind the bench seat. measures about 1.2m W x 0.3m D x 0.15m H. So I'm thinking I can make a pretty large box to fit in that area. I don't have the mackie enclosures any more, but I'd prefer something more custom to fit anyway
 
So I've managed to find the crossover circuits for the Mackies, but they were part of the amp board so I've had de-solder to remove the components. Do these numbers make sense to anyone.... 3 components, 600uf / 100V4.7uf / 100V8.2uf

In+ => branch => 600uF => 100V8.2uF Cap => Out High +
=> branch to the Out Low +
=> 100V4.7uf Cap => Out High - and Out Low -
In - => branch => to the 100v4.7 => Out Low - and Out High -
 
circuit.jpg