"I don't think it's a good idea to work on more than one project", yes I also think that's a bad idea.
Do you want to realize the ideas for fun, for profit or to learn something?
Do you want to realize the ideas for fun, for profit or to learn something?
Ask them which one you think is best/most likely to be a product they would use. Tell them it's okay to say none of them. If no one thinks those 3 are good move on to the next.