Exercising with baby?

Holly
My baby is 4 months old and I want to go for walks with my dog and push the stroller, but am worried about it being too sunny since he can't wear sunscreen until he's 6 months old. 
Is it safe to go at certain times of the day? 
(Don't want to go when it's too dark because I don't want to get hit by a car.  They are country roads, no sidewalks) 
Should I wait to go on walks until he's old enough to wear sunscreen? 
Any suggestions.  I want to exercise a bit and also spend some time with the dog since I haven't gotten a chance to walk much lately. My fiancée works during the day so by the time he gets home it's either dark or almost dark outside.