Well done Paul! A 6" dob is probably about right, big enough to show heaps of objects, yet not so much money that if it is a passing phase, you will not feel too bad. Hopefully get you hooked as well.
A neutral (or ND filter) is not essential to view the moon but it can help a bit to reduce glare and make it a bit easier. One thing you can do is have a look at your scope cover. It may have a removeable bit so you can turn your 6" into a 2" (or thereabouts!) drastically reducing glare at no cost.
May I suggest getting a good planisphere and basic star charts (see here
http://www.bintel.com.au/Accessories...oductview.aspx or here
http://www.bintel.com.au/Accessories...2/catmenu.aspx ) to help locate stuff.
Congratulations on a great buy, let us know how your son gets on with it.
Malcolm