From father of seven. . .
Simple. . . keep breast feeding! It's natural and the best source of food on planet earth for your baby is mom's milk!
The child will slowly develop a desire for mom's food naturally. Some sooner than others; and you can supplement as you go along without any pressure on you or the child.
If you're trying to ween off a three month old for other reasons like, going back to work or preservation of the breast cosmetics. . . this is not natural and anything goes. . .
Yes it's a pain for dad when mom's hooked up at the most inopportune times (mourning and night) and mom's busy; but baby is only baby for a short time. . . don't give up the magic. And through seven breast fed children, obviously, we still managed to spend "quality time" together.