If you don't have people in your family and extended family who can cover what needs doing re the kids, Care.com is a pretty decent place to find a temp nanny.
See if you can enlist your most organized, PTA-mom type buddy to organize your friends, faith community (if you have one) etc. to bring meals, 3x a week is ideal, if your spouse doesn't cook. People bring enough that you can eat that all week. Have them organize it not you. : )
Scheduling a service to come clean a couple times a month is also helpful if that's usually your job.
In general, if you have resources to exchange some cash for less stress on your spouse and whole family unit I'd totally make that exchange for a while. Otherwise, just try to spread the load to as many people as possible.
I didn't have open heart surgery but due to weakness and having 27 month preemies after my heart incident (plus three toddlers/preschoolers) this is what helped us survive. Others can help you estimate how long you're likely to need what kind of help better. Good luck!