Ya know... It really will depend on what you are looking at for the Universal stay.
November in general is a pretty slow time (Obviously, it's more crowded during the Thanksgiving period), so you may be able to get away without needing the express passes that staying onsite would give you.
You also didn't mention your party size. Is it just the 3 of you? Dad joining? anyone else? That could impact the viability of staying onsite.
The next question is what type of AP does the Step Daughter have? There are 3 levels of AP.... The Power Pass (pretty much, just admission only), The Preferred (Hotel and merch discounts), and the Premier (Better discounts and some other perks). If she has the Preferred or Premier pass, You can use her AP for a hotel discount as well as discounts on your tickets. If you don't want to stay onsite, you also could use her preferred or Premier pass for free parking.
One thing you will want to definitely keep in mind when looking at Universal: It's not Disney. By that I mean it is not a park and vacation experience that requires the same level of preplanning and micromanaging your trip. It's 'dining plan' is also very simplistic. For $XX you get unlimited meals that day from select CS locations. for an extra charge, you also can get a souvenir cup with free refills. In Practice, It's only going to be worthwhile if you (or someone in your party, since it's a per person deal, not an all-or-nothing like the
DDP) think you can eat 2 or more meals while at the park that day....Keeping in mind that due to park hours that time of year you are probably going to do so between the hours of 11am-5pm. Otherwise, it's cheaper to usually just pay out of pocket at the CS location for lunch (especially with the Preferred or Premier AP food discount).