Deer are a major problem around here and the only one-stop permanent solution is deer fencing or dogs. Obviously the right kind of dogs. I once reasoned that the fencing would be cheaper than the dogs, but I've found that over time that's likely not true.
Deer fencing has to be high -- 7', and secured on the bottom. It's expensive and you need lots of T-posts to put it up. It's going to be an effort and it will cost, but once it's up and done right it will exclude them 100%
A single 330' roll of heavy weight deer fence is $300. 10' T-posts are $7-8 each if you buy in bulk. This might be worth it to you, and if you fence a larger area you can fence a garden area as well. Around here people simply don't have gardens without it. I can give you lots of time and money saving advice about how to put up deer fencing but I would consider your costs before going that route.
Deer are browsers and they love young tender tree branches. My mature trees I've got so for the most part everything is above deer head height. They will still nibble occasionally but they won't stand up to reach higher branches when just browsing unless they are desperate. For the younger trees I have to use fence. They have done so much damage that it set that orchard back years and some trees will never be the same.
I would probably try getting poly deer fencing and making individual "cages" for each tree. Just cut a section long
enough to create a circle big enough to enclose the tree. Because they are browsing it doesn't have to be that secure. They won't push under and can't jump over if the diameter is less than a body length or so. A circle of fence maybe 8' in diameter should serve you several years as the trees mature, depending of
course on the tree. In this situation they will just see the fenced tree as an obstacle and ignore it.
To secure the circle of fence I'd think two 10' T-posts on opposite sides will be enough if you get the thicker fencing, which is relatively rigid and stands up on it's own. Of course poly fencing isn't the only option, especially if your trees are still very short. But this way you won't have to change anything for along time.
The poly deer fencing I recommend is Tenax C-flex or C-flex P but in this case you can go with the lighter weight stuff (and maybe only 6' ) because you aren't worried about a deer being able to break it. Once in a while if a deer is panicked it will try to get over my fencing but because I have the C-Flex P they usually just bounce off. You can get very cheap deer fencing just about anywhere and that may be appropriate in your case, but for me I find that the cheap stuff doesn't last. With Tenax you can get 15 years out of it and thus re-purpose it after the trees are grown.