all black widow serial numbers start with '1' signifying 1971, the only year they were made. then there's a space and a '2' which signifies it's a black widow. that serial number tag is a reissue tag (you can tell by the font.) and BW serial numbers will be in the "1 200001" to "1 204000" range. I think someone sells serial number tags on ebay, probably one of those.
that all said, that's a super nice black widow. real or fake, it's super super nice. they spent a lot of time/money to do that bike. it has the optional chrome rear fender too. and it has gray cables (a point many miss.) and the dellorto ua19 carb. that's super cool. would like to see a picture of the other side of the bike too (interested in how they did the motor.) personally i wouldn't let the kids ride it, buy them a coleman for them!