Simplify your life, and don't confuse a clean house (though it has it's merits) with being a good mom. It's been said many a time, on your deathbed you won't remember having a clean house, but the time you spent with your kids. The window of opportunity to play with them goes fast :(
Put some of the toys up in a closet so there's not so many to pick up. Rotate them every couple of weeks, they'll still get to use them all, just not at the same time...less to pick up. If your children are older than 3 enlist their help in cleaning up, they can do simple things like putting toys away.
Vacuum & sweep floors every other day, spot clean messes instead of mopping every day as well.
Make meals that don't require a lot of cooking (especially in summer) like salads and sandwiches or finger foods, cook and freeze meals like casseroles so all you have to do is heat them up and serve with a salad, and eat picnic style sometimes with paper plates and cups to cut down on cleaning. Enlist your husband to grill outside sometimes when the weather's nice and sit back.
If you don't have a schedule, make one. Schedule in "fun" time with the kids.
Make homemade playdough with them, there's lots of recipes online. Go for impromptu walks, visit a park and just play, sit outside and blow bubbles, make a meal with all the foods the same color, whatever is fun.