Grats!! Get him his own juice too haha. And if he steals your 510's, buy yourself pink batteries - that should stop him.
I recommend extra charging cables and these 4-port 2amp chargers - you can put 4 battery or PCC cables on each:
Amazon.com: Rosewill USB Travel Charger Adapter RUC-6180: Electronics
I also recommend a charging cable for work.
And when you find some thinner juices you like, Boge 510 standard resistance cartomizers are wonderful on 510. (you can't use the hotter LR ones - they can damage slim batteries). I use the standard resistance and love them. Boge are well made and the most popular cartomizers fro 510 threaded devices.
For atomizer carts, strictlyejuice.com sell precut blue foam stuffing for 510 carts - well worth the under $1 for 10
If you bought manual batteries, then you can use a 510 drip tip on the atomizer for testing juices (dripping is not recommended on auto batteries)
And if either of you decide you need longer charge
Joye 510 mega xl batteries (280mah) have 60-70% more charge but are quite long (128mm w/ a carto)
And Liberty-Flights.com (press the 20% off first on front page upper left) has great deals on Ego and Riva - the Riva 510 Lite Bundle is under $30 for 2 complete 750mah Riva 510 - 4x the charge length of a standard 510 battery
And note - if you bought auto batteries then you have to be very careful about not getting juice on the threaded end of the battery. Autos are totally dependent on a little drag sensor switch right inside the hole in the end of the battery. Gunk that up or short it with juice and the battery can be ruined. Joye 510 manuals are totally sealed metal on their threaded end.