"I've got a natural high going," the new dad, still unshaven and weary from the previous night's event but ready to jump on his Harley and roll, told PEOPLE exclusively.
Of fatherhood, Bentley, 33, said: "I've done a lot of crazy stuff in my life, but this is the wildest thing. It seems like I've opened the door to a whole 'nother universe. It's like there's another dimension I never knew existed!"
Evie, as they plan to call her, was born using natural childbirth and the help of a midwife, two factors that Bentley says gave him even greater respect for his wife, Cassidy, 33.
Natural Benefits"She set out to do things – as my wife does – her own way, and she really wanted to do it naturally," he says.
"It's an amazing way to go because it makes you get involved as a husband, just reading books and helping her go through this process," he adds. "I would have done it with all the drugs they could find! It takes a strong-willed woman and she was just amazing. You learn a lot about your wife."
Though this was his third annual Miles & Music for Kids event for the medical facility, this year's drive seemed more special. "Using Vanderbilt's services to have our child and knowing this supports Vanderbilt Children's Hospital, it means more to me personally now than it ever has," he says.
About 1,200 riders joined Bentley – who popped a wheelie as they set out – and McGraw on the ride into downtown Nashville. McGraw and Bentley, along with John Rich (of Big & Rich) performed for the crowd of 5,000 fans, and the event raised more than $300,000 for the hospital.
For the latest on star pregnancies and deliveries, check out PEOPLE's Celebrity Baby Blog!