How difficult is it to have children and spend time with them when both parents are doctors?

Thank you for anyone answering this question. My girlfriend and I are going into college soon. My girlfriend is planning on becoming a pediatric oncologist and I'm planning on becoming either a neurosurgeon or a surgeon. We are deeply in love with each other and plan on having a family together. We want to start a family anywhere from around the ages of 30-35. We know we are going to be very busy with med-school and residency and such, so we want to wait until we are sure we are ready. We want to be able to spend time with our future children and have a true family, but we are just worried about how much time we'll be able to be there for them. We would just like to know how difficult it would be to have children with both of us being doctors and how difficult it would be to spend enough time with them.