Well, you have some options here.
First off, this time of year is normally not busy and express passes will most likely not be needed. However, they are always very nice to have anytime of the year because you can skip nearly all the lines, no matter how big or small they are. Staying offsite would be fine if thats all your budget will allow.
Now, another option for you. You could stay at the Hard Rock hotel (onsite) to get all the perks of staying onsite for $190.50 a night except on Friday were the price skyrockets to $326.40 for that last night. The fact that while doing this quick search online Royal has almost no rooms and the price for rooms towards the end of your stay is insane has me wondering if Universal is excepting big crowds, which would be odd for this time of year. Anyways, your total for that option would be $1438.75.
Another option you have would be to upgrade ONE of the tickets you have purchased to an Annual Pass. The price of the room drops down to $174.00 a night except friday were it is $249. The total price for the Annual Pass room would be $1258.88. The price difference is $179.87. Another perk of having the AP (besides the cheaper room) would be food and item discounts at some of the shops, which can really add up over time. Even if you are only planning on visiting once this year, it might be worth it to upgrade one of the tickets.
I am assuming you purchased the 3-park unlimited ticket (since thats the next ticket above a 4 day) which is $174.99 Well, the AP you would need is $224.99. So, the cost to upgrade the ticket is only $50 and you would save $179.87 on the room plus all the food and item discounts. Well worth it even if you are only visiting one time this year.
Finally, if you decide to purchase the express pass on its own it will be $31.99 per person per day. Assuming you visit Universal and Islands for 6 days (leaving 1 for Sea World), your cost to have express each day would be a total of $959.70.
So, if you decide to stay offsite and purchase the express passes, you must find a hotel room cheaper than $299.18 for the length of your stay, which will not happen.
I know this is a LOT of numbers to toss at you at once, and I would be happy to explain some more in detail if you would like. To sum it up, if you think you would enjoy the express pass and early entry into the parks, then upgrade one of your tickets to an AP and book the APH rate for an onsite room. To search for rooms on the Universal website with the rate, use the promo code APH.
If you think you DO NOT want express passes, then stay offsite. Normally, if a family is considering purchasing express, it will ALWAYS be cheaper to stay onsite. Sure the cost of the room may seem like a lot, but you would be spending $160 per day just for express for every member of your family. So, if you then look at the price of an onsite hotel as if express was not free and the $160 was added into the price of the room, with the APH rate, your room just costs $19.87 for almost all the nights to stay at an amazing resort!
EDIT: Well, It seems like the Mardi Gras event starts on the 11th which normally doesn't increase crowds that much. However, every sat. night (and select other nights) they have concert FOR FREE at the parks, which would explain why the friday night stay is such a high price. The only announced concert takes place on Feb. 18th when Kelly Clarkson will preform for FREE. Other concerts should be announced really soon!
