Don't know your state specifics, but I will share our experience which was similar.
Our DS was in a private preschool/daycare, and receiving private OT and ST, but at age 4, we had him evaluated by the district (to set the wheels in motion for kinder, and to see if there was anything else they could offer us). The district started him out with a "community based PPCD program", where they came to the preschool twice a week, but after 6 months, they recommended we enroll him fulltime in the school based PPCD program. As in, "We don't think the current services meet his needs, we STRONGLY recommend he enroll in PPCD where we can provide more services).
I worked full time. The PPCD program was from like 9:15-11:30 each day. (Elementary started earlier and ended much later). I had a kid in a different private school and another one in the daycare still. There was NO way that schedule was going to work for us. It was not possible (without a TimeTurner :) ) to get the kid to/from the program and the other 2 kids to 2 different schools on time. Plus, he already was in a full time program and they were offering him only two lousy hours a day?
We weren't getting anywhere at the IEP meeting and we called for a recess. Check your Procedural Safeguards, as a parent you should have the right to do this. Basically, if you can't agree, you call a time out for everyone to go back and reassess. In our case, we had the principal call us within 24 hours to see what we could work out. Because the next step after a recess, if parents still can't agree, is Due Process. Nobody wants that, it's legal and messy and adversarial and expensive.
Turns out once we got offline, informally discussing options, I learned they could (had to?) provide bus transportation to/from the private daycare instead of our house. (Ours happened to be in district, I don't know if they must drive your child out of district or not). They also could modify the "standard" program they offered, once they realized he was a unique case. He was technically eligible for kinder, due to a birthday, and therefore when I threatened to enroll him in full day kinder, and let them figure out from there, it's amazing that they came up with a schedule that started at the same time as the elementary, and while it ended an hour earlier than elementary, they would bus him to daycare for us.
I had to keep the "personal inconvenience" of the shorter hours out of the discussion. Focusing instead on the hours of service he was eligible for, and he was currently getting out of the preschool, to how they wanted to reduce them by putting him in the PPCD program. And knowing they legally had to provide transportation for all special ed students, helped a lot.
The bus ended up picking up my kid at home in the morning, and driving literally around the corner to take him to school (our back fence is shared with the school). This helped us because he was out of my hands 20 minutes earlier than I could have walked him to school, which let me leave and take the other kids to their school on time. Ridiculous but creative thinking. He wouldn't have been eligible for the bus if he weren't Special Ed.
We kept hearing that they had never done anything like what they did for DS (changed the standard offering, extending the hours and doing 2 hrs of inclusion kinder at the end of the day) but they also had never quite encountered a kid like him. We had to focus on his unique needs, as already documented by THEIR evaluators, and the services he already was receiving, and how what they proposed would be a reduction. We also did have some great advocates on our side, the district actually has been terrific in the many individuals who provide services, do evals and advocate for him. The bureaucracy of the IEP process has been where we've had problems.
I'm sure others will recommend the Wright's Law web site and books as resources. Your district should also have its policies and maybe the state policies for Special Ed posted as well, or they provided them to you when you kicked off the IEP process. My mantra is Polite but Firm. The educated advocate parent gets more than the one who just 'goes along'. But staying friendly is so important since you will be partnering with these people for quite awhile.
ETA: Is their in-school ST the only option? You need to ask specifically if they do a Community Based program where they come visit the preschool/private school. (In our case, the private school does not have to be in district. Our Catholic school was not in district, and I know of a few kids there who had services provided by our district.) I had no idea this was an option for us at first, it's not like they advertise it in our district. But they do it. There were three community based teachers who just visited kids all over, every week. However, in our district, they only do it until age 5 or 6, then, to receive services, the child MUST be enrolled in public school to get services. That information is clearly spelled out in our inch-thick procedural safeguards and ARD guide. So you may not have an option after kindergarten age but to enroll in public school.
Good luck and hugs to you.