Michelle,
Hello again, I'm so happy that I was able to give you some ideas that might work for your family. At this time
Splitsville only takes walk-in Guests. As of right now, you just visit a greeter and ask for a bowling and/or dining spot. It's possible that advance reservations could become available, but you'll have to keep checking back for that information. They are open daily from 10:00 a.m. to 2:00 a.m. July could be crowded, so I would definitely try to get there on the early side of the evening.
As far as cost, the menu items are comparable to other Walt Disney World restaurants. A child's meal costs around $7. Many of the menu items are perfect for sharing: pizza, sushi, sliders. Bowling varies, depending on the time of day and how long you stay, but you can expect to pay $15-$20 per person.
Hope this helps. Have a magical vacation!