There are superstar sports athletes and then there are superstar sports fans – people like Jeff Siegel and his son, Spence. “We’re fanatics, over the top,” admits Siegel.

Last month, the father-son duo completed a goal to make them the envy of many: They have now been to all 30 Major League Baseball ballparks and all 30 National Basketball Association arenas.

What started as a spur-of-the-moment trip for a divorced dad and his son turned into a decade-long adventure that also prompted Siegel to write a guidebook for others. RelationTrips: A Simple, Powerful Way to Bond with Your Loved Ones Through Personalized Road Trips (Two For The Road, Inc., 2011; $14.95) makes a convincing argument for why parents and kids should spend more time together in the car.

While the Siegels chose sports teams, the Chicago dad says “RelationTrips” can be centered on any mutual interest – whether it’s jazz music, art museums, or finding the best pizza. Before every trip, the Siegels spent weeks charting the route, mapping the itinerary and designing T-shirts. And once they got home, they created scrapbooks to relive the memories.

Here – just before Siegel and his son made their last ballpark visit with his son – he tells us more about their adventures for our monthly “5 Questions” column.

1 What was your favorite ballpark?

Our top four are PETCO Park in San Diego, PNC Park in Pittsburgh, certainly Fenway in Boston, and then last summer, we were in Kansas City at Kauffman Stadium and we were impressed with that one.

2 You say the trips don’t have to be about sports. How do you come up with an idea?

It can be whatever lights a fire under your kids and gives you a common interest to build on together. One of my friends and his kids were into roller coasters. A number of people I have talked to have built it around food. One family found all these places that served nachos and they graded the nachos and did a whole scale with jalapenos. The sky’s the limit.

3 Your son didn’t mind the long car trips?

We traveled thousands of miles around the country and a lot of our road games stretched beyond the more traditional stuff where you look for license plates. For years, my son was responsible for different playlists for legs of the trip. Depending on the theme, you can do a lot with music in the car. I found these CDs that featured the 50 top sports moments in history and we would play these to death. It got to the point where Spence knew, “Down goes Frazier. Down goes Frazier,” by heart and would do this great impression of [the late sportscaster] Howard Cosell.

4 What’s so special about the car?

A lot of the stuff happens on the open road that just doesn’t happen if you take a trip to Disney World. You find there are a lot of teachable moments that crop up. I remember once Spence and I were driving up the California coast where there are all these dairy farms. I vividly remember that Spence turned to me and said, ‘What do you think those cows are thinking about right now?’ We started talking about whether cows know how long they are going to live and this lasted for hours. A college professor would call it an existential conversation.

5 How are you feeling about this last trip together?

A little bittersweet, a little sentimental. I have been divorced 11 years and my adult life has been built around my time with Spence. And frankly, when we get back, he’s headed off to college, and that silence will be rather deafening. At our last NBA arena, it really felt like we had accomplished something and I am sure we will feel the same way this month when we hit our last ballpark. But, yes, bittersweet is probably the best word.

Susan Flynn is associate editor at Boston Parents Paper. She can be reached at