Dates do not have to be extravagant or expensive. They can be as simple as going out for dessert if you don't have time for a whole meal. Go to a park and walk together. Go out to dinner when you can. I've known some to go grocery shopping then out for ice cream or something of that sort. Of course you can go all out and go to a concert or fancy restaurant, but if you set yourself up to do that every time you will find that you stop because you just can't afford to keep it up.
You should try to go out once a week. Have someone you trust watch the children so you don't have to worry about them. You need to enjoy yourself and not feel concerned about the care of your children while you are out. Remember to enjoy yourself, that is the point of the date. Talk, laugh, share with each other the things you haven't been able to share at home with the children around.
Another way to spend time with your spouse is to have a set bedtime for the children each night. This way you have some quality time together each night. Make sure you don't spend this time watching tv or on the computer or catching up on your reading. That defeats the "spending time together" part. Just because you're in the same room doesn't mean you are communicating with each other. Besides, without these distractions you'll find more opportunities for intimacy. Ever wonder why your not as intimate as you would like, think about what you spend your free time doing.
Make spending time with your spouse a priority. Too many marriages don't make it these days and I believe that is due in part to not making time for each other. I believe that if you can do this it can be the thing that could possibly save your marriage from being dull, mundane and boring. Make the time, you'll be glad you did.