Brooder options with limited space

Hi all! I'm looking to get ducks and ideally chickens as well this spring but need some suggestions for brooding options.  I'd like to get 20-30 ducklings and the same number of chickens but live in a 20ft yurt and don't have any predator proof outbuildings.  Is there any way to safely brood them outside?  

I'm going to be building mobile coops so I could move those right next to my yurt and use that but I'm not sure how to safely keep it warm enough or if it will be too stressful.  

Would it be better to only get 3 or so at a time so I can brood them inside?  Any other ideas? Thanks!!

Before replying:
do you have electricity?
where are you, what is the lowest temperature you get?
do you already have your mobile chicken coop?

If you have electricity, using brooder plates works for keeping the chicks warm. Even outside, depending on the climate/weather.
Online, I have also seen tent-like structures for chicks with integrated heating plates, but they seem really cheaply done.

https://duckduckgo.com/?t=ffab&q=heating+plate+chicken&atb=v320-1&iax=images&ia=images

Hi Andy,
I second what Hans is asking. What climate do you live in? Those heat plates are great, but are not designed for unheated space use. I had one in my unheated garage. The chickens got stressed because the heat plate couldn't keep up. I had to add another heat lamp for a couple weeks.

But if its warm enough, I have seen people use those plastic or galvanized water troughs with mesh on top held down by some weights. It wouldn't keep out a bear, but would keep out a majority of things. The closer it is to you, and your smell will help too.

I'm in southern VT zone 5b, I do have electricity.  I was thinking of getting the ducklings in May so overnight is 40'sF average.  Middle of the summer it might stay in the 60'sF overnight so I could wait for warmer temps if needed.

I don't have the coops made yet, I'm also open to building something exclusively for brooding.  Might make sense anyway since I'll be getting new birds somewhat regularly.