I think your instinct is right... maybe keep it steady and endurance while you are on the bike path towing the trailer (for safety mostly!) and then use your "ME" time to do focused workouts like hills and intervals. You want to feel good during those workouts and I bet just unhooking the trailer makes you feel like a superstar!

So maybe do one bike and one run workout with some intervals when you have time alone and then use your time with the baby to do longer runs and rides for endurance. Endurance rides are meant to build strength so I am sure pushing a baby or pulling a baby is building huge strength!

Congrats on getting hooked! I am sure you are creating a little athlete baby by bringing her along...