My grandson is with his father every weekend. This started when he was around age 1. He's now 6. He had difficulty going back and forth for the first few years. He acted out the first day with his Dad and then the first couple of days when he was back home. It seemed he was just relaxing and it was time to go to his Dad's. His Dad was living with his parents which helped tremendously. Grandma and Grandpa were experienced in dealing with a toddler. His Dad admitted he could not have managed it alone. He does have some developmental issues that, I'm sure, decreased his ability to adjust. I cannot imagine any child these ages being able to feel secure going back and forth 3 times in one week.
A 2 year old does not yet have object constancy. When he's with one parent, he's unsure where the other parent is. Can you document any behavior issues around the past year's custody arrangements? Then multiply them by 3.
An 8 year old still doesn't have a good sense of time. As an adult, I've always been confused when I had to change my schedule. I think it would work much better for eveyone involved if your ex had them for 4 days in a row instead of 2 days, not 1 day, another 1 day, not one day, and then 2 days. Each night is in a different bed, each day in a different house. And unless you and your ex work closely in using similar parenting skills, each day's expectations are different. That is just too confusing and upsetting when it comes to managing a routine. Kids need a routine and a sense of security. This plan does not provide either one.
I suggest that you get a consult with a child psychologist. (s)he can go over children's needs with you and ways to make custody more manageable. The psychologist should talk with your 8 year old so the (s) he will have an idea of where your daughter is in psychological needs.
You also have legitimate concerns re: child care when school is out, for snow days, illness. You and your ex would have to have stable child care arrangements planned in advance for such contingencies. It is unfair for him to expect you to sacrifice your work time.
This brings up another issue in my mind. Is this the way it would be? He picks them up after school/daycare on Tuesday after he gets off work. He then takes them to school/Day care Wed before he goes to work? If that's the case I really don't see how that benefits anyone, even him. It's dinner, bed, breakfast,school with no time for anyone to settle in. It feels so temporary and it does not provide for quality time together. I would see more of a point if he's off on those 2 days.
As to clothes. My grandson's grandparents and father provide the clothes he uses at their house. There is some exchange of clothes just by going back and forth but each parent is responsibile for clothing/toys/long term meds, anything used at their houses. Why should you provide clothes for his house?
Which brings up the shared custody issue. If they're half time at his house there is no child support. Is that what he's working towards? IF he has them Tues, Thurs, Sat, Sun, that's 4 days. You have them Mon, Wed, Fri that's 3 days. No child support going either direction. If you share a week end day that's still pretty close to even. Even tho the current order states that he can't modify the court order now he can go back to court to modify it later. And......he'll have proof that he has the kids as often as you do.
Knowing only what you've told me I suggest that the time that the children have with their father be in one chunk. I'd perhaps also suggest that he have just one child at a time some of the time. I'd have the order written so that there is some flexibility. I'd be sure that if there was no school on the day he's to return them that he returns them to daycare. If you had them on that day you would have made daycare arrangements in advance. You and your ex will need to work together on daycare arrangements.
I would be leary of this arrangement from 2 major viewpoints. One that it is not good for the children and 2 it looks like he's setting things up so that he can modify the support order down the line. I suggest that you offer to allow more liberal visitation times but not change the custody arrangements. and that the visitation times will be flexible as you work out what works best for the children. By doing this he could have the children for a week and then not have them for a couple of weeks and then perhaps have them for a couple of days when it fits in with both the school and his work schedule. That sort of thing. Talk with your attorney about how to best insure that actual custody is not changed down the line, unless you and your ex can peacefully and equitably share custody. With the right set of parents shared custody does seem to work out well.
I think that the most important step to take is to consult with a child pyschologist who will evaluate your situation and make a recommendation.