Braid all the way, even if it's cheap eBay braid. Maybe a mono shock leader anywhere from 100lb or more. Keep the kids fingers away tho

 Get the thickest available-used to be able to get K-braid which was great for alveys.( not diawa)

 As an ex-pro, I still had a couple of Reefmasters in the shed. Back in the day, we used 130- or 150lb mono on them, I've used that out to 100 metres or more when at anchor. If there is any tide, or drift, you need a lot of lead to hold bottom due to the line drag. And there isn't much sensitivity, ie, feeling bites, at that depth. Wouldn't even try it at 200m. Shallower water, like 40-50 fathoms, ( 70-90m), it was fine, but you still needed a lot of lead, whether drifting or anchored. 

So, last year, I got one out, serviced it, and put 500m of 120lb (?) braid on it. This was for fishing out of Winderabandi, where it would be at least 70m, and deeper. I used it a couple of times, it worked OK. Better than mono in most respects--not as much lead needed (all drifting) , good bite sensitivity. As Jim says above, you definitely need a mono shock leader, for a number of reasons.  Firstly, your mono droppers will snap off more easily on braid, the shock is really transmitted up the line, I had an unacceptable number of 80lb droppers snap on good headshaking fish, wouldn't have happened if there was more shock absorbing ability--you  get this automatically using a rod, direct to the Alvey there is none.. And you need something to lift the fish over the side on, can't do that with braid. I'd use a mono leader of at least 100lb, about 5 metres long, tie it on with a nice long FG knot.

You are pretty keen on planning to fish 200m+ with them--what type are they? The big double handers (Reef Queens?) will be hard work, but do-able if you are fit or your sessions out there are really short. The Big single handers, the Reefmasters, will be really hard work--bear in mind you'll likely have at least 250m out in that depth, it's a lot of turns to retrieve with 5lb or more of lead on, let alone fish.

What happened with my Alvey? One of the blokes up there offered me a pair of electric outfits to use while he went home briefly to check on the farm. The Alvey was never used again, and I now own a pair of electrics, Beastmaster 9000 and Seaborg Megatwin. 

Edit--and yes, be very careful with your fingers.

 I've been told that dacron is the go. 

dacron is great for snapper winches cheap and easy to get normally 100+lb is the go 

 Thanks for the feedback. Yeah I know its keen using them out deep i  will use rod and reel where I can but I think 200m is prob my max depth I could fish with my current setups could prob push to 250m but it would not be leaving alot of line on the spools prob wont fish over 300m often but they would be there just in case and I think it would make fishing for my daughter a bit easier in the shallower stuff would this stuff be alright on them or do I get some cheap stuff off Ebay.

https://www.dinga.com.au/rovex-dacron-braid-fishing-line-1200m-80lb-green-speck-32248.html

 I'm in the process of spooling my Alvey's for deep dropping as well and dacron is the go. Not sure were your located, i just ordered mine from Complete Angler Rockingham, rovex dacron exact same as you listed is $90 should be here tomorrow only ordered yesterday