Visitor Visa - B2

Hi,
Need help on B2 Visa for my parents who got rejection under Section 214(b) at Mumbai consulate on early monday morning in late November. No documents were asked & interview language was Hindi (Interpretor was present). Below is summary of interview which went for 2 minutes.

VO: Why are you planning to visit USA?
Parents: For tourism purposes.

VO: Who lives there?
Parents: My elder son.

VO: What does he do for living?
Parents: He is YYYY at YYYY (major IT company)

VO: Your son is in USA for last 5 years, why you didn't visit earlier?
Parents: My younger son was studying & was not settled. Now he is working so want to go.

VO: Is your elder son married?
Parents: Yes

VO: When did he get married?
Parents: 2009

VO: Where did marriage took place?
Parents: India

VO: Sorry we can not issue Visa to you under sec 214b.

We are 2 brothers & my younger brother works in india & unmarried. My father is in central Govt job (got NOC for travel) & mother housewife, current work location is Gujarat. We were expecting baby in late December & didn't share this information with VO as heard of rejection when they come to know about pregnancy.

Today, baby is more than a month old & thinking what is best time & reason to reapply. Should meeting my son's family or focussing grandchilren is good reason (attending annaprashan or rice eating ceremony)? Or focus should be tourism alongwith meeting son's famiy? Or want to visit son's family & visit USA since son's visa is expiring within 1 year? Recently I applied visitors visa for my in laws & they got visa.

I want to reapply B2 visa for my parents since my work visa will expire in a year & have not initiated GC. After above experience don't
understand what is best way to put up the case, what info to share & what to not to VO? Is few months old grandchild a negative reason? We live in NewJersey & my wife on dependent visa since marriage.

Any help/ guidance/ pointers from experts/ members is highly appreciated & we will be greatly thankful.

Thanks.