I think Marci-kids recommends giving both Prevacid and Prilosec 3 times/day, depending on which one your lo is on. Check out the dosing chart at: http://www.marci-kids.com/dosing.html it lists both Lansoprazole and Omeprazole as 3/day for under 3 months, I just don’t have Dagney’s Prevacid handy and can never remember which is which.
What dose is Peyton on? Are you sure he’s on a good dose? If splitting it doesn’t help, you may need to up it a little according to his weight/age.
Good luck, hope this helps!