This Saturday (July 10th) from 11am-1pm Toys R Us is having a Thomas Playdate. There will be a story, games, special offers (usually coupons) and the kids get to color and play with Thomas and the other trains on the train table.
There is usually a free gift (magnet or something). Generally speaking these are fun events if you have nothing else to do and you want to get a little air conditioning time with out actually shopping.
All Thomas & Friends Mega Bloks will be on sale B1G1 Free. Sign up for Toys R Us emails to be notified of future events such as this (and to print the B1G1 coupon). Call your local TRU to make sure they are hosting the event before you go. I know that the Niagara Falls Boulevard location always hosts these.