Grandma's celebrating her birthday — the whole family is here.
Tips
grammar
过 + holiday/date = 'to celebrate/spend ___'. Also: 过年 (celebrate New Year), 过节 (celebrate a holiday), 过圣诞 (celebrate Christmas). It's a separable verb: 过 + object.
culture
Traditional Chinese birthdays follow the lunar calendar (农历生日), but most younger people now use the solar date (阳历生日). Longevity noodles (长寿面) and peach-shaped steamed buns (寿桃) are classic birthday foods for elders.