Joint custody

My soon to be husbands ex has sole custody of the 2 kids and right now she is letting the youngest live with us and the oldest stays with her parents she works long hours at work and isnt home much at all. when she does have the kids its just a few hours and well meet or shell drop them off or ill pick them up or her parents will. sometimes shell keep them overnight but most of the time she says she gets called in to work and cant comeget them or something like that. we are still paying child support each month but our prob is she nverhas the kids and when she does she has her friend stay the night to help her watch them. she was gonna let the youngest one live with us tell he starts school in a few years now her friend is gonna move in with her and not work and watch the kids for her and clean her house. we dont understand why do that and pay somebody when they can stay here for free and shes more then welcome to come get them anytime. she always says she misses them but never trys to see them. when shes off shes out running around with her friends. so we was thinking of just doin joint custody of them. after she said she wantted them to come back and live with her she said that he could come get them anytime. knowing he cant drive cause hes legally blind. she said shes not gonna suffer cause he cant drive. do you think we should go for joint custody or sole custody?