Well, personally I think it's fine as long as you think they'll be able to sit through a show- the music is fairly modern and there's cool lighting and dancing, so it should hold their interest more than some other shows. So you can judge the content for yourself, here's the plot: (SPOILERS)
Radmes (an Egyptian warrior) is engaged to Ameneris, princess of Egypt. His father arranged the marriage and is poisoning the king so that Radmes will take the thrown soon after his marriage.
Radmes is on a mission in Nubia (south on the Nile) to conquer land, and captures a group of women to be slaves- one of these is Aida, princess of Nubia. She keeps her identity a secret (she would surely be killed if she didn't) and slowly they fall in love. She goes through an inner struggle about whether she is supposed to follow her heart or be loyal to her country. Radmes is torn between marrying this "slave" girl or following through with his arranged marriage. Eventually they choose eachother, and are buried alive together for their crime. Amneris is crowned queen and she ends the war with Nubia, saying that Aida and Radmes shouldn't have died in vain.
There is some kissing, but nothing too sexual. The death (at least in the production I saw) was portrayed by a shrinking box around them until they finally had disappeared behind it.
Have fun if you decide to see it- I saw it on tour years ago, and actually went back the same weekend w/ my mom to see it again!