Welcome to planDisney, Jason! Thanks so much for your question.
Aren't the
multi-day ticket packages great? While there are no ways to customize your ticket bundles, you will find significant savings as you continue to add on days to those ticket packages compared to the cost of one-day tickets. While ticket prices are subject to change at any time, as I'm looking at your travel dates today, it looks like you'd save roughly $58 by going with the two-day Park Hopper tickets instead of the one-day tickets.
It'll be nice to have the option of Park Hopper tickets for both days! That way, even if the plan is to visit
Disneyland Park for the whole first day, you'll still have the option to hop over to
Disney California Adventure Park for a Chile Con Queso for lunch from the
Cozy Cone Motel or to utilize the Lightning Lane entrance of the
Incredicoaster, if you decide to purchase the
Genie Plus service during your trip.
My family and I ran into a similar situation on our trip to the Disneyland Resort last fall. We had three-day Park Hopper tickets, but typically arrive a day early to focus on the drive over, and then try to have dinner in Downtown Disney on the first evening. For this last trip, I looked into adding one-day, one-park tickets for that first afternoon/evening, but found that it was even more affordable to just upgrade our three-day Park Hopper tickets to four-day Park Hopper tickets. It was so great to be able to go right into the parks, and it let us really slow the overall pace of our trip down with that extra day (since we have little ones).
I hope this was helpful, Jason! If you think of any other follow-up questions as you continue to plan your trip, please feel free to write me back directly.
Have a Magical Day,
Greg