Normalny you do not need to worry about free storage space. It should all be adjusted automatically. Having said this, Photos/iCloud Photo Libray is at version 1.0, so it might not be as polished as it should be.
1. You add and/or delete Albums and album contents as you see fit. This does not affect what is retained in your Library. Photos is not an Album, it's the Library. All Photos is a special Album, like Faces, Panoramas, etc, but it acts like Photos in that if you delete an image from it, it will be moved to Recently Deleted (sorry about this breaking the general "rules" outline before, I'm trying to get Apple to correct this anomaly).
2. Having a Wi-Fi connection should definitely be helpful in letting Photos manage free storage space and getting the images "backed up" to iCloud. I know this is not alway possible during vacations. If you anticipate Wi-Fi connection every two or three days (depends on how many photos you take per day), you should be OK. If you think you'll be without Wi-Fi for the duration of the vacation, I suggest disabling iCloud Photo Libray before leaving and clearing your local Photos Library. Just remember that if you do this, you have no backup for your new photos.
[I apologize if this is getting too complicated, but I'm trying to state things that cover all contingencies, without really knowing all the details of your particular situation.]
PS: You sound almost apologetic about being in the middle of nowhere in Australia. That actually sounds very appealing! Enjoy your vacation!
BTW, if you browse thru the links I provided earlier, now that you understand everything better, they will likely be much more illuminating.