My kids are those ages.. the only things I have purchased for them to share is that candy machine with a grabbing claw (not filled with candy though..) I wouldn't recommend this as it is very difficult.. but my kids keep asking for it and I couldn't resist.
I also have bunk beds for their My Twinn dolls (but most 5yr old boys aren't doll crazy like mine.)

Anyway, how about a museum membership, or a stack of GCs for minigolf, bowling, and movies, build a bear or a paint your own pottery place?
DVD of Cars
Board games: mancala, Blokus, Zingo, Scene It Disney, and Sorry are some of our favorites.

Also, depending on the boy (mine is very creative) a big box of art supplies. Pipe cleaners, tape, glue, contact paper, construction paper, pom poms, stickers etc. would be a big hit at my house. (They are getting this from a grandma)

for something bigger mine do play air hockey together

Are you far away? I think the best gift would be an IOU for dinner and activity with you when you see them next. They will get enough toys. :O)

HTH. Let us know how you make out.