need advise please help!

Thank you to everyone! The sixth month mark of how long we have had our foster son is coming up within a few weeks. I thought the TPR was filed already but I guess it wasn't because of changes in the birth mother's status. My question is that as we were given the update today it also said that the birth mother may be willing to consider a voluntary TPR with the conditions that she be allowed to see him several times per year and that he have continued contact with his brothers and we are to let the SW know are thoughts, issues, concerns. I have no issues or concerns with contact with brothers other than how to do so, where, and simple things like that. When I originally asked the SW about contact with birth mother after adoption she advised against it. What would be your thoughts, issues, or concerns? Right off the bat I can say that the man she wants to marry is a legal sex offender.that is a big concern and her contact being supervised is likely the only kind I would be ok with. I think the other main concern is her mental state and how she sees life without much responsibility wouldn't make her a very good roll model but I don't know how that should effect contact if she does care about him. Other than when visits where at her home and he smelled like smoke and was effected by that for a while afterwards I haven't had any issues with how he is after visits other than him wanting visits when she isn't around or contactable and than being let down by that. She has disappeared numerous times. He has lately gone to visits and come home happily and although shares little about b-mom and the visits will talk about his brother much. Thanks so much for any advise or ideas you can provide!!!