Chiba is filled with fruits. How about going to an all-you-can-eat fruits?
You can try various fruits depending on the season. Strawberries are going to be delicious in the coming season.
This website is only in Japanese but introduces farms which provide all-you-can-eat plans.
Also, if you like seafood, Chiba has vast resource of fresh seafood. I have never been to this place but the restaurant Kanaya has a great ocean view and offers all-you-can-eat plan in ¥2,910 for adults. Comes with fresh shellfish, dried fish, some meats, and sashimi rice bowl and juices.