My daughter is 9m still not sitting up on her own (Trisomy21)

She also just had open heart surgery 3wks ago so therapy can't resume for now cause she can't fully sit up assisted putting pressure on her chest both of these lean back some. Just wanted something other then her bouncy seat she could play with her toys with but still sit up a little to do. She can sit up with help but still leans to the side wasn't sure which would be a great option as the chicco is wipe able for the future but dosen't have that support needed like the Graco and I like the square bottom and the comfort straps not rubbing on her incision...The Graco has the support but isn't wipe able and turns from front to the sides just dont like it round on the bottom. And also the seat can be removed for a booster seat. If this was your blessing, which seat would suit the best? Thanks ladies so much