We used to travel the east coast down to the end of Veracruz. You're the right size. We traveled there in an 18ft TT. Much easier than with our current 24ft. Smaller is better. Good luck and have fun. The Gulf coast in the winter is my kind of place, weather and water.
Places to visit if you don't know the coast:
Papantla (Tajin ruins)
Tamiahua (has a bridge that takes you to a sandbar off shore, before the bridge we used the ferry)
San Rafael (French immigrant community, very interesting with a small French museum. A boat will take you to the island where they had a tile factory in the 1800s)