Food is a great idea, as the kids still need to eat.. That said, don't ask what they need or want, simply just do something. I found that when people are in a state of shock and grief, to think of what they need at that moment is very difficult.. Don't leave the person with that burden.. if you live close, why not make up a batch of lasagne (they can always freeze it if need be) or even some baked goods.. Additionally, you can do some gardening for them... also, yes, write a card and in it, state you would love to babysit the kids if need be.. Also, even if your friend's husband declines anything now, check back in a couple months.. right now, he is busy trying to get everything together for a funeral and deal with his kids emotionally.. the next few months, let alone year will be trying for him.. I have found that once someone dies, people are around in the beginning but seem to drop off after a month or two.... check in with the guy and his kids in a couple of months.. the first holidays will be the most difficult... send a gift or two at Christmas (if they celebrate) .. bake a pie or something for Thanksgiving.. check back to see if maybe he does need a sitter... believe me, those things count.. people like to know they are thought of ... and the kids, maybe if you get to know them better... perhaps they can do a playdate at the park with your kids.. assuming they might be close in age..
I wish them and you the best..
blessings..