If they go back after the I-94 expires, that would be an overstay, which could result in revocation of the tourist visa.
If they go back before the I-94 expires, they may be unable to use the tourist visa because of the I-130. Note that the US normally doesn't allow more than 6 months total stay with a tourist visa in a 12-month period, so if they spend 5+ months on the visa they'll probably have to wait several months to enter the US again.