Adopting a sibling group with two older bio children?

Should I adopt having two bio children?- what are your experiences - advice or suggestions?

I currently have two biological daughters. My husband and I eventually (down the road when the girls are around 12 and 8) adopt what most would consider a larger sibling group (consisting of 3-4 kids.) We want to keep our oldest daughter the oldest.

I'm an audiologist and my husband is a GM of a dealership, so finances aren't the issue, we have a Toyota Sequoia, and we are willing to renovate our house and expand it to fit everyone. We currently have a 4 bed 4 bath home.

My question is how would a sibling group feel moving into a family with two older girls in the home? I want to give a sibling group that love and support I believe all children should have but I don't want them to be unhappy? Adopting a sibling group and keeping all the children together is very important to me because I grew up the oldest child of 8. I was an adopted by my dad at the age of 6 and then the other 7 half siblings were born.

Advice? Experiences? Opinions? Thankyou so much !