Take a deep breath! I'm impressed that you brother agreed to go. That's the first step. My Mom is planning a whole family trip to WDW for her 60th birthday next year. It has been under discussion between her and myself and my sisters for over a year. I asked my 25 yo brother if he was going to come the other day, and he isn't sure. I have 3 brothers, 2 brothers in law, and a husband (all younger than me) and Disney isn't really any of their things. My husband humors me, but without the new Star Wars stuff and my insistence, he probably would be trying to get out of the trip altogether. He didn't come on the last one. My brothers in law have never been, and DH doesn't think they'd be interested in going anyway.
My brothers are a mixed bag. They've only ever been with our parents, and not at all for 10+years. None of them hate it. Although the oldest one (still younger than me) has been trying to convince my Mom to take his girls without him, since they were born. He will probably be the easiest to please on this trip, because he'll be able to see through his daughters' eyes. My other brothers.....there are a lot of other places they'd rather spend their time (vacation and otherwise) and money (even if they're not the ones paying)
They get bored at Disney....fast. During our last trip, one brother opted to spend the entirety of the last day alone, hopping to do all the rollercoasters again.
They don't care about most of the characters....if any. They don't care for being photographed AT ALL. I'm not even entirely sure that they see the theming, so the slow dark rides aren't where they want to be spending their time.
Having a "plan" is foreign to them. They also don't really mind waiting in lines. They aren't foodies, so a burger is a burger is a steak is a burger. They like a good meal, but being laid back for them translates as "not caring" to me. To some degree, this is a good thing, because they aren't going to complain about the restaurant selections enough to argue, and I know enough about their food preferences that I can make a judgement call without their input.
Basically, every single thing I do to keep things manageable with my kids is practically meaningless to the men in my family. DH has learned to appreciate my planning to the point that it limits the amount of time he has to spend waiting in line. He also enjoys eating, but he will pretty much only suggest returning to a place that he liked in the past. He also "wants to ride the elevator to space," because he saw a video online. He has no idea that getting into Space 220 is very difficult. I expect that share on Facebook will be literally the only feedback he gives me until a few days before the trip.
So, I would make a plan based on your knowledge of him, but keep things as flexible as possible. If YOU want to eat at a sit-down restaurant, then plan on it, but don't overthink it. He may like it, or he may not.
We will probably end up doing a few table services meals for our whole "week." My plan is to stick with close to the Beach Club, since that's where we will be staying. Probably Cape May Cafe, Yachtsman, and somewhere in Epcot. The latter will be for my Mom, and I will not be surprised if my brothers all bow out for one reason or another. I think my sisters will push for more dining, but I'm the one who has been the most.
I'm on the fence about whether or not we should fit in Raglan Road, since we will be there on St. Patricks Day. My baby sister is the only one who will probably care about heading to Disney Springs, so it won't be particularly convenient for the rest of us.
My plan is to ask everyone for a list of their 2-5 preferred attractions in each park and give everyone a plan based on that. I won't do this until about a month in advance, because I've learned that nobody in my family will cooperate before that point. I'm hoping to be able to divide everyone in touring groups, at least for part of the day. Meeting back up with people is also time consuming. So I'm hoping to segment the day based on interests with set meet up times to swap the children. Obviously, your group is a lot smaller, so you won't need to worry about this as much. We have a tendency in my family of all the men running off to ride the thrill rides, then being nearly impossible to track down.
In your case, I would probably give your brother a list of the attractions in each park, and have him circle the ones he's most interested in and cross off the ones he's not interested in. Even if its an incomplete list based on his knowledge of DLR, it will give you an idea of his interests and you can plan accordingly.
My family tends to take the "what do we want to do now?" approach to everything, but this is time consuming. I expect they will be fine with a plan as long as I don't push them too hard, and make sure to include what they want to do. So, if they're not going to get up for rope drop, then I'll plan most of the attractions for my little kids during that time, but make sure to get G+/ILL for the afternoon for the key attractions. Mostly, if I wait for them to tell me that they want to do something, the line will be 3 hours long, and nobody will be happy.
DH will probably end up going back to the room with the little kids by 8PM every night, but I might stay out with my older kids and siblings a couple nights.
SO anyway...keep your expectations low, then you can be surprised.