Both sentences are grammatically correct, but they convey slightly different meanings:
1. "Miss Ketchup hopes you have a wonderful holiday and A LITTLE fun!" - This suggests having a moderate amount of fun, perhaps implying that the holiday should be enjoyed responsibly and not excessively.
2. "Miss Ketchup hopes you have a wonderful holiday and A LOT OF fun!" - This suggests having a large amount of fun, emphasizing enjoyment and leisure during the holiday period.
Both sentences are appropriate in different contexts, depending on the tone and level of enthusiasm you want to convey.