Chi, usually after an appendectomy, if it didn't burst and there are no complications, most people are home the following day, but are told not to lift anything, make jerky movements etc (basically avoid clenching the abdominals) for a few weeks to avoid a hernia. Depending on his singing style, he may find it too painful to sing/rap, or he may be ready to sing, but not dance for a few weeks.
Also wishing him a speedy recovery and a cast recording right on schedule!