As opposed to Adderall, which contains roughly 75% dextroamphetamine and 25% levoamphetamine,
lisdexamfetamine is a single-enantiomer (dextro) amphetamine formula. This pure formulation may reduce side-effects, but certain individuals exhibit a better clinical response to the mixed isomer preparation, and so choose Adderall XR or equivalent generics." In other words it is apparently not as strong as adderall.
None of us can tell you what the right meds are for your child.