Have had four years of daughters birthdays from four to eight each as bad as each other. My advice is:
Limit the time Two hours is long enough
We live in a bungalow so first year they were allowed everywhere and where one kid goes they all go (even the bathroom), they especially love to be with adults. After that they were confined to sitting room. Hide all ur precious things!
Have plenty of planned activities (bit like work overplan rather than underplan) - As your only four Iv done colouring, quiz, pass the parcel (cheap stationary section in tesco with cool little light bulb toppers etc). I always avoided musical chairs, running etc as Christmas time so no outdoors.
First year I did spag bol, all seated in dining room, disaster, some made out they never seen pasta. After that chips, cocktail sausages etc, all served in one big bowl in middle of a large low coffee table and they all tuck in with their napkin wrapped fork. keep plastic glasses less than half full as u'll have spills.
Last Christmas had planned a DVD party, thought I chill out and let the TV take over. Nope five minutes in they were giggling and laughing and out came the second half of party: nail files and polish, Had roped in plenty of help and so two orderly ques were formed or u didnt get ur nails filed. Set the rules straight away.
Nice thing I do (i think) is take a group photo minute after last kid arrives, off goes OH to chemist to print it out and each kid gets one going home.
Oh daughter and I make our own invites, print them out and stick little stickers on them.