For now, use your iPod to put something on and get your children to dance. Clap your hands and do things your 9 month old can imitate, and get your two year old to properly dance. If you don't have any music, look through the TV. There is always some loony children's channel with music and dancing. They'll feel better for tiring themselves out a little, and once they've got going you can sit down if you need too. You'll get a hormone release from the exercise, and feel a bit better, too.
Then find some interesting things to make a picture with. Doesn't matter what - if you've got nothing else, look for sweet wrappers, pretty packaging, cling film, kitchen foil. Lots of textures. Let your 9 month old play with them, and make a picture with them on the floor for daddy/grandma/next door - whoever. Choose what to do - a house or a train or something, and then get some glue and make the picture. Sing some related songs, and help your 9 month old stick clouds in the sky with cotton wool or something.
That should keep them busy for the next few hours. If you get nothing else done, don't worry. If it needs tidying, at the end of it all, play the "tidy up" game, even if you have to bribe your 2 year old to help. Do it minutes before Daddy gets home so it's pretty tidy when he walks in. Who cares what happens afterwards. If it gets messed up again, he can help to tidy it.
When they go to bed tonight, take a few minutes for yourself. Have a glass of wine/hot chocolate or something and just take a second to recoup. Stop thinking about what needs to be done, and calm down for a minute. Then build this calming-down time into your day. 20 minutes to read a magazine between the children going to bed and you putting a wash on or something is essential to your wellbeing.
Finally, if your DH complains, tell him that you will prioritise the children over everyone else. They are unhappy, so they are whining. You've set impossible standards for yourself. If you can't get things done while entertaining them, look at other options, like getting a cleaner. At the end of the day, it's not important. Being a happy, engaging mummy for your children is.
PS - I always found a schedule helped with whining. It might be too early for your 9 month old, but your 2 year old could help. Print pictures of different activities - playing in the garden, going to the ducks, playgroup, nap time, making cakes, blowing bubbles, drawing pictures, watching a film, doing nursery rhymes with all the moves etc, and then laminate them. Stick velcro to the back and to a piece of paper, and after breakfast in the morning help to choose an activity. There is a reason they do this at nursery - it lets them know what to expect. Any free time you get, put books out and read a story. When baby whines, change the game, or sing a song, or do dancing. Anything to distract him and stop the noise, so it doesn't drive you insane.
I hope this helps a bit. Look after yourself. You don't need to be superwoman - and the HV will know that most people clean the house seconds before she arrives. Your children being happy is the most important thing, and you feeling human and happy too. Then the house.