Hi, A 12 inch front wheel won't solve the problem of the rear spokes coming loose or snapping.
If you want the bike to be taller, and providing there is enough room in the swinging arm to fit a 12 inch rear then upgrade at the same time as you make the modification. Buy some decent spokes - any reputable motorcycle dealer will know where to get them from - or talk direct to a wheelbuilding specialist. Are the rims distorting? - it could be they are not strong enough to carry the weight or stand the pounding.
My guess is a good set of stainless steel spokes would cure the problem.
PS - fitting a 12 inch front will make the bike much more stable over or through a rutted surface. A lot of kids in the auto class use 12 inch fronts because it makes the bike much easier to hang on to.
MC