You pay a premium to have the tickets in hand prior to game day, while accepting some risk in exchange for (maybe) a better price buying on the street. Sellers will be out there, but they are almost all pros and you never know which way the market will break. I used to buy cubs tickets outside wrigley all the time, but had no pressure because we lived nearby and could always go do something else if we didn’t find the right price. Ask your hotel concierge if they have any - unlikely, but worth asking. If you do decide to buy tickets at the park, best to leave your wife and kids in the restaurant or hotel and go looking on your own. If they see your family in tow, they know they got you. Bring a seating chart and take a hard look at the tickets before buying. Wrigley is family friendly, other than perhaps the bleachers on a nice sunny day, which can be quite a party. Bathrooms are an adventure so keep your kids close by.