My baby just turned 4 months. She has yet to learn how to sit unassisted but I would like to get her something that can occupy her and also free up time for my helper. Her current rocker is getting too small (the ingenuity) and I don't want her to constantly just be laying down on the play mat. I'm thinking of buying some of the following for her, which ones are recommended? - bumbo seat - jumperoo - play yard - baby bjorn bouncer (read that she can sit in it till age 2?)