If they are being paid for their services, which most of them are, then I don't think a tip is in order. What DJ or photographer would provide their services for free and depend on tips to get paid?
Maybe I'm misunderstanding this question.
ETA: I do think they should be included in the dinner.
Formerly Ford1224
We must always take sides. Neutrality helps the oppressor, never the victim. Silence encourages the tormentor, never the tormented. Elie Wiesel 1986