In addition the post from drdance I would also mention that just because an exercise does not look like dance or ballet does not mean it is not dance/ballet specific there are many strengthening methods designed to illicit are certain stimulus and therefore deliver a certain adaptation. Working with vocational students in the S&C studio and in the gym I have noticed certain trends that Dancers are eager to recreate ballet or dance in the gym. This is not always to their advantage because overall strength and power, for example, are developed in a specific way. Therefore I would recommend strength and conditioning with a strength and conditioning coach with a background or experience in dance. However, a reputable S&C coach in any field would have the ability to enhance a young dancer physically and gain the desired outcomes.
Under the age of ten I would recommend general athleticism is just as important as dance specific strength.