First you need to define big front wheel. If you are talking 21" or maybe even 23" it may ride okay and installation isn't a problem, the 23 will require engine guard removal. Larger than that, like a 26 or a 30", the frame needs to be cut and raked, triple trees need to have additional rake and the front tubes need to be extended to make room. Ride and handling will be changed for sure. To install a 26-30" front wheel is $10,000 and UP. Is it worth it for a kids big wheel? Only you can answer that for yourself.
For me a bagger is meant to be ridden, not just posed upon.
But that's just my opinion.