It will be a safe combo for sure but it depends what you are looking for. I disagree with the first poster, only because my hippy has consumed cannabis for years now ( smoking leaf, concentrates, and edibles ) and he can tell you that if you are new to edibles or have a low tolerance, a strong edible can destroy you.
However now a days my hippy wakes up to a couple bowls with his breakfast of toast usually slathered in more cannabutter. He has a dugout he takes with him throughout the day to medicate. So if he was you, really the only thing out of the ordinary would be the DXM dose!
In that case he says go for it. DXM can be intense and the body load troublesome at times, but it sounds like fun to him. Eat your edible and wait a couple hours to gauge the strength, after you stop getting more medicated, take your DXM and wait till it peaks. At that time decide when and if you still want to smoke. Easy as that.
Marijuana goes with my hippy's everyday life. If he trips on anything, he smokes too. If he rolls, he smokes. If he takes stimulants, he smokes. If he goes out to eat with his whole family, he smokes. Then again he does not see marijuana as a drug, rather a medicine. To each their own.