Without knowing your budget I'd recommend a Supreme 2000 with a 15 horse prop drive. The Supreme will make the transition from the Little Red to the White. You'll want prop drive due to all the moss on the Little Red. 15 horse is light enough to handle and not offset the boat too much yet powerful enough to handle the occasional 4 people.
If you are going to fish primarily on the Little Red you might consider getting an aluminum boat and just renting what you want for the occasional trip to the White.