Argo cargo bakfiets kit $900 - note there is an attachment piece that fits on the bottom bracket that attaches the bike to the spar coming from out back of the box so you would need a rear hub motor ebike as you can’t use the Argo with most mid drive or front hub motor Ebikes. It does not currently come with a rain canopy, some owners have jury rigged a cut down trailer canopy but you might consider buying a blaqpaks custom rain canopy for $450. The box arrives with bare plywood so you would need to paint on a couple of coats of urethane.

You could DIY convert a bike using a TDCM IGH motor which is a direct drive rear hub motor built around a 5-speed Sturmey IGH, from Grin Tech for $1,000. Add a cheap PAS cadence sensor or pay $250 more if you want a bottom bracket PAS torque sensor, it can use a 36v or 48v Battery (say $500) as the Grinfineon controllers and the motor can take either voltage - ask for the 20a controller and 36v battery if you want to keep it a Class 1 or 2 ebike under 750w. Donor bike, preferably one with semi horizontal drop outs so you don’t have to add a chain tensioner to convert to an IGH, something already fitted with an IGH would work, example 2017 Breezer Downtown 8 ST from an independent Breezer dealer would be $475, or the sliding rear drop outs on the SOMA Buena Vista Mixte frame should mean you would not need a chain tensioner added to the derailleur hanger.

Alternatively you can motorize the front wheel on the Argo box with a geared hub motor threaded into a disk brake compatible 20" front wheel and mount two 6ah power tool lithium batteries plus the controller on the back of the box, choose any donor bike with an IGH and it would remain a pedal bicycle when you detach it.

If you wanted a trike attachment consider the AddBike available from a dealer in Montreal for $1,400 with a one child box with rain canopy, this would be shorter and considerably easier to store because it doesn't have a support spar so unlike the Argo the AddBike does work with mid-drive ebikes, but it costs $500 more and is rather short with a 77lb load limit vs 150lb for the longer Argo, so your daughter would age out of the AddBike faster.

Cost should be $3,000 to $3,500 for a 2 wheel bakfiets kit or 3 wheel trike kit with IGH, electric assist, rain canopy, plus the ability to remove the front box, tie it up outside your daughter's school, attach your front wheel and ride off to work on your bicycle or ebike.

You could motorize a fully built bakfiets with IGH like the Wike Box Bike ($1,600 +shipping) or Bertus Cargo Bike ($2,000 +shipping) with either a 20" front motor wheel or the TDCM IGH rear hub motor but you might need to add a front or rear brake if you lose a coaster, drum, or roller brake in the process. The Bunch Bikes Swift is $3,300 plus shipping for the electric version with rain cover but you would forgo the IGH.

Probably the cheapest cargo ebike would be the Yuba Mundo Classic longtail from REI plus a bafang mid-drive - you could build this combo for around two grand but you wouldn't have a rain canopy unless you could jury rig something like an ebay canopy onto the optional Yuba Monkey Bars (+$250) like this https://www.xtracycle.com/blog/ride-on-rain-or-shine/.

If you can, try out as many different kinds of cargo bikes as you can find. I went to a family biking show-and-tell earlier this summer and got to try a Riese & Muller Packster, Urban Arrow, and Xtracycle longtail back to back, all handled differently when loaded.

I have a cheap Chinese short box bakfiets and my father in law has a Madsen with the mid drive. They are not functionally equivalent. The bucket on the Madsen is bisected by thtr rear frame and wheel. That makes the rear bucket a lot less useful than it looks. The frame feels whippier, too. He bought his before the mid drive was a factory option but I think the systems are the same. That part seems to work well.

Also, I really like having my kids in front where I can see them and interact with them.

But in summary, I’d take a cheap knock-off front loader over a Madsen.