Veg to Flower Timeline Question

I have two plants, each with 4 nodes, that I would like to take into flowering because of a timeline issue (I am leaving for a week in late July). While I absolutely know that they may not be finished by that time, I would at least like to give myself a fighting chance to see them finished. Is it ok to put them into flowering after 3 weeks?

Sure, you can do 12/12 flowering from seed if u wanted to.