My friend and colleague Ben Orozco, emergency physician at HCMC, and toxicologist with the Hennepin Poison Center, put together this very useful chart of intervals in pediatrics.

This is particular useful when children are poisoned with drugs and medications that prolong intervals:

For those who want more detail on normal values for the Pediatric ECG, including amplitudes, here is an excellent full text pdf article from:

Rijnbeek PR et al.  New normal limits for the paediatric electrocardiogram.  

2001 Eur Ht Journal 22:702-711

Here is one table on intervals from that paper with more exact intervals (since free full text pdf is online, I took the liberty of putting this one table here):