Turning my house rabbits into garden rabbits - need advice

I have 4 free roaming house rabbits but two of these thrive much better outside than inside, so I have decided to let these two move outside and be free roaming garden rabbits fulltime.

Garden is completely secured. I have bought a hutch for them which I will make more rabbit friendly and then I hope they will use it on rainy and cold days.

But what is your advice for me? Should I give them food with more fats so they can gain more weight and protect themselves better during wintertime? Should I have several insulated houses placed around the garden? Basically, I am a completely rookie when it comes to rabbits living outside, so I just need all the good advice you can give me.

Are you completely free of rabbit predators such as foxes/dogs/birds of prey/cats?

If not then they would really need a secure enclosure rather than totally free roaming.

Rabbits have so many enemies; it's a lovely idea to let them be "free" but for rabbits this is quite often costly. Your rabbits need to be safe, at night especially, as you would treat a child, imo. It isn't difficult to get rabbits to come in in the evening, just wait until then to feed them and they will be in like a shot. They shoulldn't need any more food when living outside, just lots of hay and their normal food. I think bunnies are healthier outside but then I've never had house rabbits. Our homes are not alwaays rabbit friendly.