A few weeks back, my husband and I decided we would take a vacation this summer (8 hour drive) with our three kids who are 5,3, and 1. I've since been on the hunt for travel toys and games, items I might be able to use to make our trip easier and more fun. I found this great contraption...but didn't really want to buy one for $22 for each of my 3 kids!
http://www.amazon.com/Star-Kids-Snack-Play-Travel/dp/B000KJBFC8I made note about the things on this tray that I liked and wanted to implement in MY tray.
*edges so things don't fall off
*straps around carseat
*wipes clean
Then, there were a couple things I thought of that this tray did not have...
*magnetic
*dry erase board
*pockets
Here's what I did: purchased a pack of 3 cookie sheets at Walmart that come in graduated sizes. (My kids come in graduated sizes too so that works out!

) Purchased 2 magnetic dry erase boards, and 6 sheets of felt.
Total spent: $4 cookie sheets, $5 dry erase boards, $1.20 for felt, $5 for nylon strapping $15 for all three.
Here it is installed on the carseat...

Not installed...

We recently had to take a trip that in total was about 6 hours one way...so we tried out the trays. They worked out well.
This is my youngest using hers...I did NOT put the dry erase on hers. It's not really something she enjoys yet.

In a nutshell, we cut slits in the sides of the cookie sheet for the straps. I attached velcro to the straps and sewed the straps to the cookie sheets. I removed the dry erase boards from the frame...which left me with a very flat sheet of dry erase metal. I glued that to the cookie sheet. So, not only is the cookie sheet magnetic, but so is the dry erase board.
I have a full tutorial on my website. Oh yeah, the trays worked out well for eating as well. They wipe clean easily and are flat so food/drinks don't fall off.
http://www.vibrant-designs.net/2011/03/touring-tuesday-travel-tray-tutorial.htmlAll in all, I would consider this a success!