new job W4

I just started a new job. I am a single parent (separated but divorce drags on). I always file HOH status for my taxes. Trying to determine what to put for the W4 withholdings. I have one child who turns 19 soon and who just finished freshman year of university across the country (she's living home for the summer). I have claimed her in the past on my tax returns. I have 14yo son too who lives with me 100%  
I'm trying to understand what to put for my W4. Because of my single parent situation I'd like as little withheld as possible from my paycheck with the understanding that doing so means I won't get a larger refund on my taxes.