It all depends on the size that your Doodle will be at full growth...some are small (I have a standard that is 19 inches and 40 lbs) and some are larger...I have heard of doodles getting over 100 lbs...so it is impossible to say what size you will need without knowing the size of your dog.
The crate should be large enough for your dog to stand and turn around comfortably. You can get extra large crates with dividers in them to make them smaller while your dog is growing.
I know I can get a bigger crate, but I dont have the space for one, at the moment Otto is 21 inches to the shoulder and 21 kilo in weight, he can stand and turn round but for not much longer.
My other dogs slept in beds I did not use crates so this is all new to me. Last night Otto was sleeping on the floor in the dining room I thought I would take a chance and leave him as he was comfortable, but in the early hours he panicked and came looking for us, he was only happy back in his crate. Has any other person had this problem is he going to want to be crated all of his life?
You could leave the crate door open if you think he will be okay outside the crate...this will give himthe option of deciding where he wants to be. Usually they love their crate and will go there to rest and be safe.