Just tell them what we tell Suhaina........."Beta it is a matter of personal preference."
If you train your kids now that some questions don't have a right or wrong answer................then they will already KNOW the most reasonable response. That way they'll figure it out on their own in the future and won't have to ask. You'll be developing independent decision making skills in your kids! LOL. ;)
1 is 4 yrs old .. n other is 4 1/2 yrs .... how shud i explain it ?