Just got back from a weekend there. Bunch of lads so didn't pay too much attention to the family oriented facilities. We rode Mabie (red), Kirroughtree (black), and Dalbeattie (red), the group was mixed fitness levels and ability but all got round fine.
I'd say avoid the black at Kirroughtree if you're wrist is still a bit dodgy, it's pretty technical in places so depending on your confidence/pain levels it may be a bit much. The red sections we rode were nice though. Mabie was good - smooth and swoopy so good for a sore wrist, but only 17km so unless you go round twice maybe not that suitable.
I'd say go for Dalbeattie if it's close enough - it's about 25km and there are short black sections which you can take if you're feeling good. The red was a good mix of fast rolling, roller coaster sections and rockier more technical sections. No idea what facilities are there as we just parked and rode.