I think a 4 year old easily could be too rough for a chihuahua puppy and even an adult dog ....especially when parents are not watching :( Smaller dogs just can't take the normal treatment a child could dish out. But it depends on the household and children involved along with parental involvement and concern for everyone's wellbeing.
As for destroying furniture, I'm not sure exactly how a 5 pound dog could gain such control over a household as to chew up a sofa

;) a real 'mighty mite' ;) :D They're not really heavy chewers, but are in proportion to their size.
hth
toodles