I work almost strictly from home, and Im a single mom to "The Hoardes" as well. It`s been tricky, but I`ve been able to establish a few things.
One thing Ive found is to have an established place to work, and NO KIDS allowed no matter what! Whether Im in there or not... its Moms office. (( A corndog stick in my expensive printer taught me THAT lesson )) Also.. I established a set time for working. When I was married and had the help, the kids knew that after dinner, mom was off duty and "at work". Now that Im single, Ive resorted to staying up all night, but it worked well when I had someone to help with the kids. ;c)
I also had a special drawer of stuff for the kids that they were only allowed to use while I was on the phone. Treats (( hey, Im not above bribery )) and markers, stickers etc... if they would iterrupt while I was on the phone.. I just opened the drawer. Of course now that theyre older.... ;c)
Not sure of your exact situation... but thats what worked for me!
I have a sitter help me with the kids when I`m trying to work. She`s a retiree and isn`t too expensive - plus I`m usually here to as supplemental help to her. I don`t really have any strict boundaries, but my little guys are 4 /1 2 and 1 1/2. I also have a couple of p/t helpers and I farm out things like printing, payroll and bookkeeping. All of these combined really help.