Jason Aldean also shares with PEOPLE that he and his wife Brittany have been "throwing names around" for their little one on the way

Brittany Kerr Aldean‘s second pregnancy was an extremely welcome non-surprise.

“It was definitely something we had planned,” Jason Aldean tells PEOPLE exclusively of the timing of their baby on the way.

The couple welcomed 7-month-old son Memphis on Dec. 1, and the country megastar and Field & Stream brand ambassador is also dad to two daughters from a previous marriage: Kendyl, 11 next month, and 15-year-old Keeley.

“After having our son, we knew we wanted to have two kids,” says Aldean, 41. “I have my two older daughters already, so after Memphis was born we knew we wanted to have another one pretty quick — to go ahead and knock it out and have one that was a little closer in age to him.”

“I would much rather knock it out now while we’re used to having one in diapers and formula and all of that,” he adds. “I think it’s tougher when you get out of that and wait a couple years and then have to go redo it all. … We just wanted them to be close in age, and we figured we’re already in that mindset now, so why not?”

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Jason Aldean and family
| Credit: Jason Aldean/Instagram
Jason Aldean, wife Brittany and son Memphis
| Credit: Brittany Aldean/Instagram

The “You Make It Easy” hitmaker reveals he and Kerr Aldean, 31, underwent in vitro fertilization once again for their second child.

“We did IVF with our son, so we had to do that again with this one,” he tells PEOPLE, adding of the baby’s sex (which they are keeping a secret for now), “We knew what was going on.”

Although the parents-to-be went into this pregnancy similarly to Kerr Aldean’s first, there have been some big differences since finding out they were expecting again.

“With my son, Brittany didn’t have any sickness at all, but with [this] baby she’s been pretty sick for the last few weeks, so we’ll see,” says Aldean. “Maybe she’s starting to turn the corner a little bit, but it’s definitely been a different kind of feel for her this time.”

RELATED VIDEO: Jason and Brittany Kerr Aldean Welcome First Child

Aldean says his daughters are hugely into sports — specifically, volleyball and softball — and that Field & Stream is a “natural fit for me” considering his outdoorsy upbringing.

On Friday, the singer even surprised fans with tickets to his current High Noon Neon tour at a Field & Stream store in Kennesaw, Georgia, hand-delivering the tickets, taking the winners on a personal shopping spree and presenting them with $500 gift cards.

“I grew up loving the outdoors and hunting and fishing, so [Field & Stream] was an easy fit,” he tells PEOPLE. “I love what they stand for as far as traditions and everything being about family and passing things down from generation to generation, which is how I got into it — through my grandfather and dad.”

Aldean tells PEOPLE that he and his wife have been “throwing names around” for their little one on the way but “don’t have anything solid just yet.”

“When Memphis was born, we had that name picked and we liked it, and we knew early on that it was going to be that, but we were leaving our options open just in case something else came in that we liked better,” he recalls.

“And then we started ordering stuff and putting his name on it, so we were like, ‘All right, well, I guess that’s his name.’ But with this one we really don’t know yet,” Aldean explains.