Tons of greens + Superfood type supp. Zero sugary crap. Laugh a lot and watch comedies regularly(helps, seriously).
Re grief, -its a big deal and nasty shock so you're going to feel shit for say a month afterwards and nothing's going to change that. -ie accept this/dont beat yourself up trying to fight it and just focus on keeping up with your responsibilities and being a good dad.
Also dont retreat, get out the house and keep yourself busy.
As above watch a bit of comedy and hang around friends who you have a laugh with and upbeat. Stay the hell away from friends who can sometimes be a downer. Do outdoor activities with the kids and hammer it in training.