I'm assuming you are checking in the same day? Then no problem whatsoever. In fact, even if one party checks in a week later, no problem. At least in my experience.
When the first party checks in, have them make sure the Cast Member sees the notation that the two parties want to be next to each other. The rooms have already been assigned so it should already be taken care of for you. If not, have the first Cast Member see what they can do. When the second party gets there, they can check in with any Cast Member as their room is already assigned with the first party making sure the rooms are next to each other.
Couple of experiences. Two cabins and one campsite at Fort Wilderness. I checked in first and actually checked in for both cabins. I was told the cabins were next to each other and was given the keys for both. One was ready (not ours) and the other was wasn't (ours). But since we were there first, the Cast Member just switched the two cabins around so we could get into one right away. I checked on the campsite and it was as close to the cabins as it could be. That party checked in totally on their own.
Two rooms at All Stars. We checked in a full week before the in-laws. I requested adjoining rooms (we didn't need connecting). We enjoyed our week and then when the in-laws arrived, I went down to check on their room. They were in the connecting room next to ours. What was even more impressive was that this was during the Christmas/New Year's week.
I wouldn't worry about it at all. And no reason for all of you to be there at the same time to check in with the same Cast Member.
