I feel your pain!
My DH is pemenately attatched to his computer too, although I am nearly as bad. But he doesn't "hear" me when I talk.
Now it's gotten to the point where I treat him like one of the kids. I tell him what time we are leaving. Then I give him a 30 minute warning, 15 minute warning, 5 minute warning. And, when it is time to go, I tell him I'm leaving. If he doesn't come, I go without him. I *hate* going places without him when I've planned it as a family thing, but I'm happier to at least get to go.
I'm sorry you had to miss the picnic, and I hope your girls will understand when you explain it to them. Maybe you can take them to a park for a special picnic with Mom sometime?