Your hotel is seems to be way too low for anything clean or safe at $250.00. Don't forget to add taxes and fees. Anything that low attracts long term residents that have socioeconomic problems.
Sixteen hrs driving down and back on your Mom too with the kids is exhausting and difficult. Only people use to that drive are safe to try it. I really think you need to consider two more nights for a stay driving each way.
Our 16 hr trip ends up two days of 12 hrs because of traffic, restroom stops, and food. We drove 12 hrs stopped and then drove 12 more the next day....I swear I will never do it again! Not when airfare and luggage is $200 round trip.
One breakdown with the car and your trip is ruined.
The other cost is $15 for parking x 5 $75 at Disney Parks you need to add.
The food, consider the drinks, meals is more than $300, that is $10 a person, a meal no options.
Unless you only eat one counter service a day and bring drinks to the parks, or drink a lot of water. The rest is off site sandwhiches, pizza and cereal.
Park tickets- You can get on the MouseSavers.com newsletter with a link in it for the lowest cost tickets.Disney at the window are higher, plus tax is not included on the web site. The five day will still be about $1,200 no park hopping.
The Parks, your brothers are going to enjoy the animal kingdom and want at least half a day if hopping at the Hollywood studios. Star Wars. Animal Kingdom Dinosaurs, are things boys like over he Princesses. They may want to do adventure cards game time too at Epcot or MK. They will make their own boy type memories, not relive yours.
Our budget trip driving was $2,200.00 for four and we had annual passes so no tickets and we stayed off site condo $750 for 8 nights. We ate in the room, had picked up take outs keping park meals to a minimum. I took a small cooler in with drinks on the stroller. With AP no parking fee. One park counter service a day, just over $15 for meal, drink and something cool during the day.
We couldn't tell the kids no souvenirs, they didn't go crazy, but it adds up. Autograph book, pen, and little things like keyring, small stuffed animal.
T-shirts are $25-$39.00, bought those on sale before we left.
Try a pool day not a beach day because of tolls, extra mileage, and exhausting for Mom fitting in DTD at night. But, what would you do there, just walk and look? A meal at Earl of Sandwhich is affordable.
Why not save up another $1,000 over the year, find good flights and rental. The drive is exhausting for amateurs. Let the boys earn money for their self, it's really not that much more of a savings to drive that distance. I would have to save a lot more than $400 to drive.
A general budget for us a nice trip is $100 per person per day for 4 of us.