I bought these for my eldest son (3) and they just arrived today. He was quite excited as he knew they were coming. After all the hype of going through the set, pulling out the medalion, looking at all the coins, he enjoyed taking all the stickers and sticking them on his Dad the most.
And of the coins, the only one he was really interested in was the Gordy the Gecko medalion.
As for the coins, I would only give them an Ok. Actually probably an almost Ok (should this be a new grade?). They are weakly struck without a lot of detail and require a bit of twisting and turning in the light to get a good look at them. I think most would pass on a purchase if the coin was in hand.
But then again, they aren't meant for serious collectors, or even adults for that matter, so they may appeal to the younger market. My son wanted them so he could get coins in the mail and share in what I do, so if they ignite some spark of interest, then they have done something good. However, I think I could have achieved the same result by sending my son something a bit nicer myself.