A couple of things...
We are talking about one of the most sensitive parts on a woman's body. There are very few of us that have vaginal births that don't have tearing or an epesiotomy, much less having said area stretched. And our bodies do not look they way they did, EW! I love Bill Cosby's description, "try pulling your bottom lip over the back of your head, THAT is giving birth!".
So, take all that plus a thing that yanks on your breasts in not an always comfortable way, wakes you up every single night, throws up on you, has to be with you all the time...SHEESH! Who wants to be romantic?? Darlin there IS hope! It is a thing called time and patience.
Be good to you. Decide once a week (since it is difficult) that you are going to be romantic! Alot of it is mindset. Friday nights are "date night", for example. Play with the baby, get them well fed and tired. Give them a nice bath and put them to bed!
Tell hubby that date night is the night for romance and you want to be babied the way YOU are gonna baby him!
Tidy the house, make the bedroom romantic with candles, music and your perfume. Take a nice long shower, wash your hair, shave your legs and imagine what your relationship USED to be like and how you want it to be again.
Have a nice dinner, whether it is take out or something special you make, ready with the table set nicely. Candles and dim light are awesome! Don't talk bills or anything heavy, all wonderful small talk.
For the physical part there are oils that help (I am NOT going into descriptions here). And ask your husband to take his time. Look at every hair on your husband's head, his shoulder, look at the color of his eyes. See every perfection and imperfection and with all your heart LOVE it!
Marriage with kids is a balance. All your energy goes to children when you have them, husband and self get left behind.
Take time to take care of you and your husband, even if it is only one night a week. You both will look forward to it, even if all you look forward to is the romance and he looks forward to the um "fun". Learn to appreciate other aspects of your relationship and each other. And even if the sex doesn't go beyond that day it will remain a special day for both of you. =)
Good luck!!