The only way to get your husband to go is to talk with him and arm him with knowledge about cruising.
Cruises are great fun. Honestly, your daughter is probably too young for it to be particularly memorable for her - but it would be a shame for your husband to miss out.
Essentially, it'd be just like going on any other vacation with a toddler - you have to be aware of what they're doing all the time and sometimes that can distract from the experience of the trip. But they do have the Camp Carnival which, when we cruised last year, had accommodations for children 2 and up. This will keep your daughter entertained if she's already used to a day-care-like environment; and they have babysitting at night (from 10pm to like 3am). Note that camp carnival is not open all day - they take breaks, and the timing of those breaks can be sucky sometimes.
The cabins are smallish, but I've stayed in cabins with three twin beds (some that pull out from the wall like bunk beds) and other cabins one kings-size bed (two twin beds pushed together). Your daughter may have to sleep with the two of you.
The food is abundant and the room service is absolutely free.
Find out what your husband objects to and work together to see if the two of you can come to an agreement. If he flat out doesn't wanna go, then you go and have a great time and don't feel guilty about it!