My friends were going to do the split stay route 3 nights Universal and 5 nights at WDW. After running the numbers she said they were over their budget a lot. So I suggested staying at one resort for all 8 nights then either renting a car or using Uber to go between. WDW was offering Free Dinning which worked in their favor, so they did 8 night AOA family suite, with PH tickets (6 days) and
DDP, They got their tickets for Universal from Undercover Tourist. Used Uber back and forth. On the 2 Universal days, they did breakfast in the food court at AoA and lunch twice and dinner one night at Universal, used snack credits for a night time snack once back at the resort. The credits they did not use the days at Universal they used on a signature meal, at California Grill... So for their family it worked out. You just have to play with the numbers and see what works best for your family. She also like only have to get settle in the room once and did not waste time moving from one place to another.