Staying at the universal hotels is great as you get early park access as well as the the universal express passes. Breakfast at the hotels can be expensive, but they might do a “per item” buffet where you can pay for just a bagel (or whatever), but still about $5! There’s a Starbucks and a Cinnabon at city walk, and lots of snacks in the parks.
You can walk from the hotels to the parks - takes about 10 mins.
Usually only one park is open for early access, so check which one you’re heading to (they are right next to each other)
It’s worth wearing lanyards with plastic wallets for your hotel room keys which you need to show for park access and can scanned in the express pass line.
Alot of universal rides require you to put a bag in a locker. Small lockers are free, but bigger ones cost a few dollars, so worth considering how big a bag you need.
Frozen butter beer is the nicer option IMO, but still super sweet, so only get one for the family.
Food options in Universal are not great. Mythos (islands) is genuinely good, but as a table service restaurant is a bit pricier. Leaky Cauldron (diagon alley in universal) is ok. At City Walk (the restaurants opposite the parks) we like Bubba Gump shrimp (but only good if you like seafood), and Cold Stone creamery for ice cream.