Don't spend any Turbine Points on anything for at least a few weeks. ALL the level 1 and 2 quests in the game are completely free to play; adventure packs don't start until level 3. And then there is still plenty of free content from levels 3-12, so you don't need to buy anything for a while.
I wouldn't spend $60 on a 1-month VIP trial for all four of you, or even $15 for just you. The 500 TP is nice, but $20 gets you 1950 TP during double bonus point sales, so $15 for 500 is not a good deal.
For new players, here's the packs I recommend they start with, in order, and why:
#1: Red Fens
The fens include good sets for just about any build in the game, so if you have a static group of four (a melee, a divine, a rogue and an arcane, maybe?) you'll all have nice sets to get from the Fens. Also, it's cheap, meaning this feels like an attainable goal for new players. It's a level 9 pack, so it helps out right as the free content starts to thin out. Plus it's an epic pack, making it valuable at endgame.
#2: Attack on Stormreach
This pack has some of the best first-life melee weapons in the game, fantastic monk gear, a great set for divines (sora kell), and it's super fun and well constructed. It's a level 13 pack, which is nice because F2P content essentially ends at level 12. It's also pretty cheap, making it a reasonably painless second pack to get.
#3: Vale of Twilight
Everyone needs vale for greensteel crafting. This is an expensive pack, but it really should be your third purchase. It's level 16, and attack on stormreach will be able to get you to vale, and vale in turn will get you to 20.
#4: Secrets of the Artificers
This level 19 pack has crazy good sets for virtually every build in the game. When you first hit level 20, equip your secrets sets and maybe some greensteel from vale, and you will be ready to face epic content.
#5: MOTU Expansion base package
The expansion is well worth it, but it's expensive. The retail price is $30 in the DDO Market (not the in-game store), but there have already been 75% off ($7.50) and 50% off ($15.00) sales so far, so look for one of those.
These first five purchases can be delayed until you actually get high enough level to run them, are an affordable introduction to the game, and will enable you to gear yourself reasonably well along the way. And of course, never buy anything at full price. Wait for sales of at least 20% off.