I would try dancing with them. Call me crazy, but Richard Simmons has some really good ones called "Sweatin' to the Oldies, Boogie Down the Pounds, and Party Off the Pounds."
He's funny, full of energy, and kids love them because the music is so much fun! I remember doing Sweatin to the Oldies in Highschool. It was a great work out that didn't feel like a work out.
Congrats on getting past the first trimester! I'm in my third, and the activity I went with was just brisk walking. I take my 9 year old with me sometimes, and we "gossip" it's a great way to bond with her.