ronx,
what exactly is your son doing?
I have two DD's 5 and 2. I am satisfied with what they eat - no problems there.
My 2 yo can use a spoon, but tends to put her hand in the dish. I am gently encouraging her away from this. She can also use a fork, but is only just beginning.
She spills some food from her plate, and I make sure she has a bib to avoid her clothes getting stained.
My 5 yo to my mind has more significant problems. For example, she doesn't really use a knife yet, and often uses her hand instead, and I would be interested in what other people's 5 yo's can do. I am unsure whether her will simply go away in time, or whether they need active involvement. I have been cracking down on them, but frankly not to much effect. I am probably going to change my strategy to firm rules, clearly explained + sanctions, but no nagging at all and see if that sorts it out.
In answer to the OP, if I wanted a really nice lunch, I'd someone to babysit. Otherwise, I'd expect a bit of mess, take some toys, and try not to allow the meal to last too long. As you can imagine, I don't get out for a meal much but I am quite a decent cook, so that doesn't matter really.