When I'm away for more than about 4 days I will usually trailer my horse to my coach's place and put him in training so he is getting ridden (he is at PSG level dressage, competing at CDIs so also very fit). For less than that though I would probably just leave him out in his field. He is used to 24/7 turnout, does not throw shoes or need to be booted/wrapped and thrives living outside, being able to exercise himself. And his field is a hill so moving about he still does some strengthening.
This fall I am going to Holland for 2.5 weeks and I don't know if my coach will be able to take my horse. In the case that she can't I will likely just have the barn staff bring him in at night, out during the day. There is no one at my barn/city that I will let ride him. If I am lucky I might be able to convince someone to bring him in late (ie 8pm as opposed to barn turn in time at 2pm). And then at least he will have someone looking at him every day.
Were I in your situation, and if my BF was confident enough to handle my horse, I would take up his offer on turning the horse out. Start turning the horse out for an hour or so a day about a week before you leave, then your coach or whoever can ride him Monday Tuesday, and your BF can turn him out for a bit on those days too. Then by W/Th/F/S he should be used to the turnout, and tired from being ridden. IMO he probably doesn't need to be wrapped up like a Christmas gift, and simply leaving some rubber bell boots on him 24/7 so your BF doesn't have to deal with them, or teaching him to put bells/no turns on would alleviate a lot of the shoe-pulling worry. If he can gallop around jumping without killing himself, I think he will be fine in a 1/2 acre turnout pen, any smaller and I think your worries are justified, but a decent sized pen he should be fine.
Good luck and have fun on your trip!
They say money doesn't buy happiness -- well happiness doesn't buy horses!