I wouldn't say anything. Some people might spend $30, some $5, some in-between. Others may not bring a gift, though I know it's generally am unspoken expectation for a kid birthday party. There's always a chance people will decline the invite due to not being able to bring a gift, and that's too bad, but I still think mentioning gifts or lack of them is bad etiquette and unnecessary.
2/4/13 at 7:29pm