Hi there! Welcome to HCM!
Hope your wife's post delivery period was/is uneventful. The " rich' diet that you mention, is something which is possible anywhere and anytime. Your wife needs to breastfeed the baby for at least 6 months; and to do that effectively she would have to physically and mentally healthy. Plenty of water, fresh fruit juices, mixed vegetables and grains should do the trick.
Breastfeeding your baby regularly will keep the weight off, and in a healthy way. Light exercises like walking can also be stated, after consultation with your doctor.
As for multivitamins post delivery, they need to be started only if your wife seems to deficient in them. The apt amount of vitamins would be obtained from most healthy foods like broccoli, spinach, beef etc.
And lastly, please ask your wife not to
stress on
weight loss. This is a beautiful period in your lives, which needs to be enjoyed to the fullest.
Good luck! Hope this helps!