I don't think it will be a problem. You aren't really checking in a curb side (since you did that at 24 hours), you are really just dropping of the baggage. When you check in online, they will ask you how many checked bags each person is taking. They should then mark the itinerary as having 3 bags, I don't think they will necessarily need to see all three folks when you drop the bags off.
The only problem I could maybe see is they see 3 bags for 2 people, and try to charge you $20 for bringing a second bag. I don't think this will happen, but it might.