1. Get a bucket and do some sort of theme, park day, etc, put in magic bubbles, sunscreen, sunglasses, and a note telling them where you can take them. A cheap plastic bucket with shovel makes a nice start for a beach day theme present. You really can put the present in one bucket for them to share...
My 6 year old niece has one and LOVES it. I think her mom paid around 12-15. The 8 year old might like it as well. My girls at school are in to Hannah Montana and High School Musical things. (3rd grade).
As for the 2.5 (boy or girl)? I have a 3 year old DD and she loves anything DORA or girly such as dress up things. Not sure on the boys.
So much depends on their interests and what they already have.
For the eight year old, a subscription to American Girl or another magazine; a craft kit (beads might be risky around the youngest)
art materials, gift certificate to the mall, DVD, a trip to the mall to choose a shirt
Hi! I have a 6 year old, and I happen to teach middle school. Let me just say that the middle school kids thought I was so "cool" when they found out that I also have some webkinz that I play online. Actually it's a family affair, as my husband also plays them online as well. I have 8, he has 10, my daughter has 16.
And, in my town there's a shop that sells them for $12.00
Also, my 6 year old loves BRATZ, Barbie, Princesses.
But, I guess you may want to find out what they're into first.
I also liked the first poster's suggestion of a theme park, (if you can afford that, some parks can be pretty pricey...even for a day).
Is there a Build a Bear Workshop near them? If so, you could do Bear Bucks Gift Cards.
They come in cute little boxes. That is something they could all go out and do together during the hoiday vacation week.
I agree with this one (I'm to the point I want one!!) My friends' daughters have them and they're fifth graders (10-11?) so I'm sure the 6 and 8 year old would enjoy them.
As for the 2.5 year old... at that age they love pretty much anything.. but personally, I'm an Elmo lover (the red fuzzy variety, not the document projecting variety ), so it would have to be something Elmo..
I agree with the other posters that Webkinz would be a great idea for the two older girls. For the younger girl, I'd recommend the Pucci Pups. I just gave one to my friend's 2 year old for her birthday and she just adores it. Her mom says that she takes it everywhere! Here is a link to target. I've also seen them at Walmart. They come in many different varieties.