Check the wording on your agreement. If it is really vague, then rather than guessing what will happen, you should ask the other parent if you can have them the whole weekend.
Tell them that it would be nice for either of you when it's a long weekend to have the kids for the whole weekend. This way, you both can make plans accordingly for long weekends. The worst they can do is say no. If you wait and wait, you'll stress out over what plans you could/should make. If they say No, just go with that and don't make a scene. However, if they say No, that sets up the precedent for future long weekend visits for the both of you.