I would highly recommend a peak detection charger - they are worth the extra money. But you don't have to get anything outrageous - just about any peak detection charger will work for your situation. Dynamite makes some decent ones that are very reasonably priced. For inexpensive stick packs like a venom 4200mah, the vision peak 2 is just fine. It's only around $40 and is very easy to use. If you have any plans up possibly upgrading to Lithium batteries, you might want to look at something else. But, at $40 for the VP2 you could just as well wait to get a LiPo charger if/when you upgrade.

If you or your son ever decide to start racing and/or buy expensive high end batteries, then you should look at getting a really nice charger so that you can monitor the charge and tweak settings to make the battery have optimal performance.