Hi Laila,
Welcome back to the Disney Parks Moms Panel! I am sorry to hear that you had some difficulty boarding rides with your boys. I have twin girls, so I can empathize with your riding dilemma.
According to the
Park Rules, children under 7-years old must be accompanied by a guest 14-years old or older to board an attraction. When the girls were younger, if we could ride together in the same ride vehicle, we were fine. I could not, however, ride with one in one ride vehicle and then allow the other child to ride in a separate ride vehicle. I have never seen an official list that identifies these rides but I have reviewed a freely accessible blog post on Touring Plans that includes a guide to Walt Disney World attractions and seating in Magic Kingdom. Whether or not you can ride with the boys by yourself really just depends on the type of ride vehicle for each ride and how many passengers each ride can accommodate.
Another example for us is
Space Mountain. I could ride with both girls in one ride vehicle because the ride vehicles seats three.
Astro Orbiter, on the other hand, only seats two per ride vehicle, so my husband had to ride with one girl while I rode with the other when they were younger. We managed this dilemma ride by ride in the parks.
When our girls turned 7-years old, it opened up a new riding universe for us! Honestly, I was a little hesitant to let them ride alone but they were ready to be independent.
Laila, I trust that your next visit will be spectacular and that the boys will find themselves surrounded by pixie-dusted fun!
Magic, memories and Minnie Mouse hugs,
Donyell