Kate, thank you for visiting the Disney Parks Moms Panel.
I love the close-proximity to the parks and the extra perks of staying at a Disneyland Resort hotel.
Unfortunately, there is no guarantee you'll be able to view the fireworks from a Theme Park view room at the Grand Californian. You may have a view of California Adventure and may possibly catch a glimpse of World of Color. You may also have to upgrade to a club level room to potentially get a view of the fireworks from your Grand Californian room.
If viewing fireworks from your own room is vital, I recommend a Premium View (looking towards Downtown Disney) at the Disneyland Hotel. Upgrading to a Club Level room will also put you on a higher floor, enabling you a better fireworks view. I had the pleasure of viewing fireworks in the E-Ticket Club on the 11th floor of Adventure Tower at the Disneyland Hotel, with snacks and a drink in hand, ooh-ing and ahh-ing to the accompanied music. Access to this exclusive lounge is granted to Guests who have a Club Level room.
Prior to your arrival, call the hotel to reiterate your request for a room where you can view fireworks from. Cast Members will try their best to accommodate your request, though it is not guaranteed depending on various factors affecting room assignments.
I hope this is helpful in planning your upcoming trip to the Disneyland Resort. Please visit me on the Panel again if you have further questions.
Have a magical day,
Kiki