I could do this as £75 for 2 tier or £45 for single tier but would need you to provide the Lego bit for the topper. I can add characters for £7 each or you could provide them. I would put the cake on a larger board and have Happy Birthday etc written on the board.
Birthdays are a big deal for children, and we like to celebrate it appropriately. We make a big deal out of it. Our children get a party for family and close family friends (the 'family party'), and then they get to invite a few classmates for another party (the 'friends' party).