Son Ace Knute, 4 1⁄2 months, adorably made his red carpet debut Saturday at a Dillard's store in Dallas during an event celebrating her Jessica Simpson Collection.
Simpson, 33, protectively held on to the chubby-cheeked infant, who looked sweetly stylish in head-to-toe gray, including an unbuttoned shirt with the sleeves rolled up and super-cool baby Jordan sneakers.
But big sister Maxwell, 18 months, didn't let her little brother hog the limelight. The towheaded toddler, dressed in leopard leggings, a graphic tee and faux leather bomber from the Jessica Simpson Girls collection (which Jessica and Ashlee co-design) hammed it up, waving and dancing with her family as the hometown crowd of over 1,000 watched, an onlooker tells PEOPLE.
The mother of two, who's been posting sneak peeks of her shrinking physique online, didn't disappoint either, flaunting her figure in a short, striped dress.
Also on hand to lend their support for the line were Simpson's fiancée Eric Johnson, mom Tina, her younger sister Ashlee and her boyfriend, Evan Ross.
"Everyone was in the best mood, having fun with fans and each other and so excited to be home in Texas," the source adds.
Hey homies come and meet me and @JessicaSimpson tomorrow in Dallas at Dillard's in North Park Mall from 1-4pm!! Ye-hawwww— Ashlee Simpson (@ashleesimpson) November 22, 2013
– Jackie Fields & Kathy Ehrich Dowd