I stayed at the Holiday Inn Maingate. I would not recommend it and would not stay there again, but the walk to the parks was fine. The Doubletree, Holiday Inn Express, and Hyatt Place are in the same general area. I might look into one of those hotels for another trip.
You do have to cross a major street, but there are crosswalks and traffic lights with walk signals. Once you cross that street, it's actually a nice relaxing walk, well-lit at night and it has good sidewalks the whole way. You enter Citywalk through the valet parking entrance. It takes about 10 minutes if you walk at a decent pace.
It's an easy walk, but it is a 10-minute walk, be sure everyone in your party is able to walk that far. You will also need to keep a close eye on small children while crossing major streets.
If you have a rental car, one thing to know is that not all of the close offsite hotels have free parking. Be sure to research parking charges ahead of time and add that to your room rate when you are pricing the hotels. If you decide not to walk and instead drive your rental car to the parks, you may get stuck with paying parking fees twice - parking at the hotel and parking at Universal.