I would be interested in 5 total dailies. Reason is: you need to have at least 1 option for each mode, to encourage ppl to try that mode.
So: 1 option checked: you get 3 dailies of your option, and 1 more for each of the other 2 options, just in case they are easy which would encourage you to try that option.
2 options checked: 2 of each, and 1 more of the option that was NOT checked.
3 options checked: hmm not sure actually lol! 2 of each except for one option which only has 1.
This would work for 7 also, if more options for the 'main' mode are needed.
edit: and of course, only reward the first 3 that get completed.