Keeping them separated during the day is not a problem. We put up a second pen last summer when we were thinking about getting drakes for the ducks so that we could separate the flocks by breed. We just hadn't gated it yet. That was done last night. George has been sleeping with the adult ducks for about 2 weeks now without incident. He is a little pushy with them at times during the day but never mean. He just gets excited and likes to chase them around the yard (kind of like we do when we round them up at night). I am not worried about the ducks, they actually adjusted to the ducklings faster than I thought. Maybe because they already had to adjust to George. My adult Khakis & Cayugas are about a month apart in age (we lost the first Cayugas to illness and immediately replaced them). There was a lot of back and forth when they were introduced to each other and they weren't really one flock until after their first winter together. This time it only took a couple of days before they quit testing boundaries and started ignoring each other. George was just being George and claiming ownership of everything like a 2 year old. (I brought out tomato out to them one day, and George tried to lay claim to each piece I tossed even though he doesn't even like tomatoes). The ducklings were a little more skittish around him, but everyone was coexisting well. As far as the food and water go, they were sharing, George would just shove his way to the front of the line if it suited him. He eats or drinks his fill, and then wanders off. Caligula's death was a huge surprise. I actually wonder if it wasn't the fact that we had two pools that day that was the instigator. Our older pool had sprung a leak that morning and we weren't sure if it would hold water all day (but if we dump it, the ducks see that as an opportunity to dig a giant hole) so we filled the replacement pool as well and planned on tossing the old one after everything was emptied that night. Part of me thinks that the with the two pool situation, the babies (or at least Caligula) got used to having all day uninterrupted pool access and George suddenly decided it was his. That maybe Caligula didn't leave and George took things too far.
As for Martha, George seems to be interested in her (or at least curious). I think that he recognizes that they are the same species. She just ignores him. I think part of it is the size difference, but that is getting smaller each day as Martha is now bigger than the ducks. That is why I thought penning them up together for at least part of the day might be a good idea. At some point they will all need to be in the shed together unless there is a way to winter the geese outside and even then, George and Martha will need to coexist. We will of course keep the Geese completely separate from the ducks during breeding season, we don't want any issues with anyone being aggressive toward each other or toward any babies we may let them hatch.