I'm going to show my age, but back when I was AD CG, I was directly offered a Special Agent position with US Customs (now DHS) because I had a bachelors degree and 10 years active L/E experience. CBP and HSI both take directly from CG ranks, but you need to make sure you concentrate on Maritime Law Enforcement Operations after graduation. Your major in the Academy really has no bearing (unless you desire to do vessel inspections, cyber, or MSST (maritime safety and security team)), more important is attending advanced L/E schools and performing CG Law Enforcement missions. What
@Bash On said is right, unfortunately 99% of the positions in those units are enlisted billets, the officers are usually command and do not actively do L/E. Most CG L/E Schools are enlisted, and having a bachelors degree with CG MLE School training and active L/E participation is what DHS and other federal L/E agencies look for. For the most part, once you make senior O-2 or O-3 you do not get to "actively" participate in boardings, investigations, or arrests, you supervise and coordinate.
This is NOT to say you CANNOT go from CG Commissioned Officer to Special Agent in a Federal Agency, but it is actually easier to lateral over to DHS, Justice, or Treasury and do Law Enforcement as a 6c (Federal Law Enforcement Officer) but is age restrictive because of the mandatory retirement age factor coming from enlisted CG than Officer. This is mostly because of the "obligated service". You will have five years minimum, and maybe two or three of those as a Boarding Officer before being advanced beyond the "boarding team leader" into supervision or command positions. Remember in the CG, O-2's often get command of smaller cutters and shore stations, but do not actively do L/E, so you are not gaining the ongoing experience of the senior enlisted (E-5 and up) L/E types. But a lot of being offered a position in Federal Law Enforcement is having a "hook", ie: someone needs to pull your name off the qualified list and actually hire you. If your dad will still be active CBP leadership, it probably will not matter whether or not you are even L/E qualified, as long as you pass the exam and make the qualified list. If you don't care about the 6c aspect there is no age issue, and usually no L/E training or certification needed.