I missed Mothers Group Wed because I was recovering from a cold and DD has just gotten one and when I had my MCHN appointment yesterday got the 3rd degree (apparently because it was CPR but hey, I'm a nurse and used to teach First Aid!). Apparently another Mum went although she had a cold but kept away from the others. SO, my point is, do what YOU are comfortable with. What would the other Mum's say if you went?
On a side note, I moved a lot as a kid and often missed out on saying goodbye to friends (for various reasons) and really resented it. So, if you didn't want to venture out with DS - is there anyone who could take DD for you? Being able to say goodbye will really help the transition and provide closure like you already said.