Meeting DS ex for lunch

[Callmeaneggimfried]

I'm in London for the weekend, posted some pics from yesterday. DS ex messaged me saying if I spare hour or so we choice meet for lunch. They were together 15-18, broke up as DS cheated and they were going to unis at opposite ends of the country.
Her mum passed when she was young so I felt very maternal towards her, she was lovely. They are now both 24/25, DS is with someone new as is she but I've kept her as a friend in Facebook/instagram.

I have a spare couple of hours this afternoon, she's offered to meet for lunch, I want to go.
DS hasn't replied (and probably won't before the opportunity has passed) but I'm not sure if it is unfair on DS to go, they broke up years ago but it took him a small life time to get over her.

WIBU to go to lunch?

He does get to decide if he wants a relationship with his mother though.

I don't think I would without mentioning it to my DS first, so it isn't a no but it is a 'not immediately'.

This is one of the downsides of SM - people who would have historically been oblivious to your movements now see posts and thus situations like this arise, when no one is really that motivated to stay properly in touch.