EP: Get Together -- The club system is great for gathering Sims; I often set up a club just with the young adult and up family members before I move them out so that it's easier to gather them for family events, and to keep them united after the parents have died. And it's expandable as new content is added.
GP: Spa Day -- I would have said Vampires but I know supernaturals aren't everyone's cup of chai. While Spa Day doesn't really offer much for kids (I wish they could do yoga to build Motor skill), it's got a lot to offer everyone else. I especially like to have my elders take up yoga and meditation so it gives them something to do. And there are some beautiful Build Mode textures and objects that are great if you're into building and design.
SP: With the addition of toddlers, I think Kids Room is the best of the stuff packs; much of the content in Kids Room coordinates well with what we got in the toddler patch, so it's a seamless transition from one age to another. I also like Movie Hangout because there's a lot of colorful furniture, and you can watch the movies on any TV (you don't need to use the big screens that came with the pack) and they're fun to just sit and watch along with your Sims. If you tend to play wealthy Sims, I'd go with Vintage Glamour for the butler and the furniture, especially the new double beds and the full length mirror (which has 3 lengths to suit any wall height).
