There are by-laws written in every HOA contract. I suggest you and your parents should read the HOA rules and regulations that everyone must abide to in your neighborhood development. The by-laws are created to prevent things that could possibly lead to decreased property values. Because you live in a residential neighborhood, it could be that commercial vehicles (owned by homeowners) are prohibited from being parked in the driveway. If that should be the case, then perhaps it is time for your father to park his vehicle in the garage. Otherwise, if the rules and regs state so, he can and will be fined.
If the rules and regulations specify there should be no commercial vehicles parked, then your dad is breaking the rules. Some associations say "no pick up trucks". But, the standard of luxury vehicles is an opinion only. Depending on the accessories and model of the Sprinter, those vehicles are well over 40K....not your typical economy vehicle's price tag. At the end of the day, it is a delivery van and that may be an issue with the HOA, especially if it has any graphics/advertising on the vehicle.
Again, read the HOA contract of rules and regulations to get your answers.