For a family of 4, I don't think a Sienna is necessary. My family (5) had a 2006 Sienna and only put 22,000 miles on it in 5 years. We used it for long driving but it was so impractical for short trips like to the mall especially when only going alone or with one other person.
But if you really want a family hauler, the 2015 Highlander is another alternative. It gets 2mpg city over the Sienna's 18. It allows Seating for 8 (LE model) and is probably more enjoyable to drive than a non-SE Sienna. Overtime I think you'll be more Satisfied with the Highlander. I recommend test driving both of you really can't make up your mind. But test drive the Highlander first, & if you like it, don't bother testing out the Sienna to save time and maybe save the salesman a little more time. They'll appreciate that and give you a good deal
