Dad here with two teenagers. What I'm about to suggest goes against my enjoyment of p99 but when you're mixing kids into the EQ world stuff changes.
I played on the live tutorial with my kids. My daughter was 8, son was 6. Both were reasonably proficient readers. The three of us would talk about what each class and race was like. I wish there was a page like this when I talked to them:
http://wiki.project1999.com/Character_Races
So the three of us chose our races and classes. They chose what sounded fun. I chose what would be needed to round out a decent group. On the live servers for the tutorial which race didn't matter much. Complimentary classes though helped a lot.
The live tutorial was great for a few reasons: Small zone so if you want to afk or corpse run it's easy. Lots of quests with good rewards for the level. Plat generation is great. Very easy to get into trade-skills if you desire. No need to worry about I.P. exemptions and bans. You can run free to play accounts all you want. Once you "graduate" the tutorial there's Crescent Reach with more quests. You can stay here through your 30's.
Things I did to keep my kids safe. Their UI had only a few windows. One window had spell spam, one for melee spam, one for quest spam and one for faction. Everything else went into one window that as minimized. I had them on permanent AFK mode with a reply "Send tells to *my toon's name*". They also never saw shout/ooc/auction or emoticon. Yea, last thing a young kid needs to see is some edgy ass-hat do a /em wants to fill your cherry cobbler with whip cream.
Good things that came out of playing EQ with my kids. They very quickly learned a lot of math. If one bag can hold 8 staves and each staff is worth 5p5g how many bags full of staves do you need to make 150pp? Also economics, do you want one bag full of staves or one breastplate? If your kids are struggling with reading then having them read through a quest for an awesome reward gives reading a purpose rather than some boring shit they were required to read. This can also be something of a carrot when it does come to school stuff. If they want to play EQ with dad after dinner they have to have ABCXYZ done before-hand.
Last and best reason to play with them; bonding time! Yea, it's only pixels. However letting your kids into your world will create something fantastic. You can still keep your p99 account just for yourself but three (or four if you can convince mom to play also) people sharing an hour here and there together is a ton of fun. Relying on each other to succeed is great; also giving a valiant effort together but dying anyway is valuable as well.