No experience with that rod or outfit ... but, slower action isn't "all that" IMHO. Moderate fast to very fast action tip will be fine, and I actually prefer that range of tip action over the "slow" (parabolic bend) action rods (you don't have to set the hook as hard with the faster action rods) . And yes they do have a soft membrane in the mouth, but many have been hauled over the side with the hook hanging on the lip. The trick is to get the hook stuck in the roof of their mouth.
4-6lb test line is fine, too. Either one will get the job done. Everybody has their favorite brand, and mine is Vicious Panfish Copolymer hi-vis 6# test (currently), but I have used Stren, Trilene, and other brands in 4# & 6# test over the years.
to Crappie.com .... and to the wonderful world of Crappie angling Hope to see your reports/pics, and hope we can be of help to you and your son.