Heather

I hope you don't mind but I am going to ask a few questions

I am not seeing you as trying to take control of your children or take that control from your H. I am seeing you as scared that your kids S4 mainly prefers your H. And you are fearing a loss of your children and there need or want for you. Sorta like he gets to do everything with them and I get to do nothing why wouldnt they prefer him. Am I close?

This is not fair you should be allowed bonding time with your children. You should be able to take both of your children to the beach for a enjoyable day.
Why wont he let you.
I see maybe two reasons from your thread
A. he is trying to punish you through the children. He knows they are your weakness and by controling S4 and not allowing him to spend time with you he knows he is hurting you.
B. He also has a fear that your children will want or need you more then him So he is pushing you out of the picture.This thought comes to me from you making a statement earlier in the thread that your H wanted to be able to start making more decisions about your kids. Now he wants to make all concerning S4.

Either way you look to end up loosing if you continue to allow this to happen. And I am not talking him taking your kids away I am talking about the lack of emotional bonding time on your part and the large of amount of it with the kids on his part is going to make the scales off balance with need of both parents to have healthy relationships with the children. He may feel this was tipped in your favor before and may only be trying to even the weight or he may purposly be trying to tip them in his favor. I cannot tell. Only you know what is inter reactions with the kids were prior to all of the problems and how much dependency they had on him prior to the problems. My guess is there was some or the kids would be more reluctant D2 in paticular to go with him now.ie Crying reaching for you ect..

Question is H always home when you are with the kids. After work it appears so if he always picked them up. What about weekends? Does he ever work on Sat go off with friends to fish anything?

If so take this time for just you and the kids. Dont do laundry vacum the floors or those things. You have plenty of time to do these things when H is in contol or charge of the kids. Use this time to tickle read a book or pack them in a car and whisk them away for a ice cream cone.
With S4 in paticular this will build on your emotional bond. Not saying if daddy is gonna take him somewhere all of a sudden annouce well mommie ws going to take you for ice cream as a treat while daddy was gone. Thats putting him in the middle and more then likley gonna start a fight.
But take what little individual time you have for you and your children and make it a good time. Just a suggestion.
You may already do these things with your kids and just have not relayed that to us. Or you may not get alone time. Not real sure just wanted to throw it out there.