I also wanted to reply to the couple of posters commented on my reflection about making (and potentially having to cancel) plans based on not knowing he was coming home.
I'm not saying that people wouldn't be understanding if I canceled plans because of it. Or that I wouldn't drop everything willingly in order to spend time with him. Again, it's just my own preference. If at all possible, I'd rather not have made the plans in the first place. Sometimes it might just be about inconveniencing people, or it might actually be a matter of money spent.
Again, no matter what it is, of course, I'd do whatever I needed to do to spend the precious time with him. But if that is at all avoidable, well, I'd just rather avoid it.
Based on the OP's update, I really do have to wonder if her mother is going to be ok with this as a surprise. At this point, I would keep mum since as the OP said, it's not a sure thing yet. But really, when it does become a sure thing, it will probably be good to really evaluate how your mother might feel about this.
I do agree that if your brother insists it should be a surprise, you should not go against that. Just that in my opinion and in my experience, this is a surprise that should be engaged in unless you and your brother are pretty confident that everyone will really be ok with it, and maybe most especially your mother.
I was going to be #6 (I think) with 'no'. I would hate it.
I love the anticipation as much as the event itself, and onetime someone wasn't coming home for Christmas, I spent the entire month crying at every mention of Christmas (I'll Be Home for Christmas was the worst song ever.) At that time, I had no one else to think about, like my other children and grandchildren, so that would have made a difference. If I had thought there was over a 50/50 chance he'd be there, I would want to know.
As soon as he gets on the plane, I would want to know especially.
The surprise is a surprise at anytime. We were just as surpised that we were getting twin granddaughters early on as we would have been showing up at the hospital. We were just a surprised that we were getting 25th and 40th anniversary parties in the planning stages as we would have been showing up for dinner somewhere.
Regarding the bolded above, I so agree with this!! Yes, exactly.