Well, with a mare you have bred that recently....I wouldn't do any intensive riding. Nothing that would make her sweat a lot. You don't want the mare's body temp rising too much.....it can kill sperm (but your mare has already ovulated so that's good) and could terminate an early pregnancy. Not saying it will...just pointing out that it can. Sperm and embryonic vesicles are temperature sensitive. We like to keep mares relatively quiet (ie, only turned out into paddocks) until they are confirmed 35 days pregnant. After that...you can use/work them as if they weren't pregnant, until they get very huge.
But, if you think that she will pace and work herself into a slather just because she is alone back at your place, I would ride her. Good luck!
A good horse is worth more than riches. ~ Spanish Proverb