Then seal the kid party invitation either by rolling the paper into a scroll and tying with gold or purple ribbon, or if you want to get fancier, melt some red wax and fasten to the invitation (possibly adding an "H" to the wax while it is still soft).
And if you are really all bored up to write it out on your own you can just print one of the printable invitations given below.
Oh so now that your invitation is ready. Lets get started doing some decorations, well if you really want a grand and has got no issues to spend a lot over the decorations then well you can make your house look like the great hall by using cardboard made walls and stick it on your walls with help of a tape. Use poster board to make signs for "Diagon Alley", "Professor Snape's Potions class", "Hagrid's Hut", "The Great Hall"... And match the locations to your activities. You can also make a cardboard sign reading "
Well, that’s it then. You are ready to rock the party. And yes. If you have any harry potter merchandise or any posters well, then you can add them to your walls or your shelf’s.