I am a bit confused as my family worships demigods and want me to do the same but I like to worship only Krishna. Am I disrespecting the demigods?
Certainly, you are not disrespecting demigods. However it is better to know how to properly worship demigods and Lord Krishna.
In the Bhagavad-Gita, worship of different demigods or rendering service to them is not approved. It is stated in the seventh chapter, twentieth verse: “Those whose intelligence has been stolen by material desires surrender unto demigods and follow the particular rules and regulations of worship according to their own natures.”
The Supreme Lord, who is known as the Yajna-purusha, or the personal beneficiary of all sacrifices, is the master of all the demigods, who serve Him as the different limbs of the body serve the whole. Demigods like Indra, Candra and Varuna are appointed officers who manage material affairs, and the Vedas direct sacrifices to satisfy these demigods so that they may be pleased to supply air, light and water sufficiently to produce food grains. When Lord Krishna is worshiped, the demigods, who are different limbs of the Lord, are also automatically worshiped; therefore there is no separate need to worship the demigods.
So yes, followers of the Krishna consciousness movement believe in the demigods and they offer their due respects to them. In fact, they offer respect to all living beings, seeing them all as servants of Lord Krishna. But they worship and love only the Supreme Person, following His instructions in the Bhagavad-Gita to give up all varieties of worship and just surrender to Him.