Yup, they don't die of orf. But it can become very unsightly and clearly very very sore. It's generally lambs which suffer the most - if it's on your land then your ewes will have some immunity to it.
Be aware however, that the vaccine is live, so once you use it, you
do have orf on your land. So do not vaccinate unless you are sure you have orf.
And of course if you bring on recently vaccinated stock, then you bring the disease on as they will be shedding live virus.
We vaccinate if we have been getting significant levels of infection, so have vaccinated for the last couple of years as we had a lot of work washing faces and so on the year before that. Up until then we'd just had a few cases, none very severe, so hadn't been vaccinating.
Yes you can reduce the level of problem by keeping the lambs on ground where there aren't prickly things - thistles and gorse being two such - which will make lesions through which the virus can enter. And while you just have one family affected, I would be tempted to separate them if practical as they will be shedding live virus and increasing the risk of others getting it. Once more than a couple or three families are affected, it's a bit Canute
Lesions on the ewe's udder could have come from the lambs - if they're bugging her for milk, making small cuts and splits in the teats with their attentions, and have orf on their faces, they can infect her. If she's fit and well, it shouldn't be a big problem as she should have a level of immunity, but it can tip them into mastitis if they are under pressure already - for instance, short of milk, rearing triplets, etc.
Every year we discuss human infection with orf. A lot of us have had it, once, and it was unpleasant but really not terrible. However there are a few who've had it and it was horrendous. We've also run a poll to see if we thought that people who get cold sores maybe don't react so badly to orf, but that was inconclusive.