Technically: The kid has an attitude towards his mother, and his mother can't do anything about it. It is very hard to translate. 我真拿你没办法 = "Yeah, I'll do it."... in a very grudging tone of voice. 我对你很无奈 = "I guess there's nothing doing."...again the tone of voice is important.

一小孩对他的妈妈撒娇或胡闹，他的妈妈对他无可奈何 A child is acting like a brat or is horsing around/running around and his mother feels completely helpless. 我真拿你没办法 or 我对你很无奈 I feel completely helpless against you.