diet/food to help with overflow constipation

[PinkDaydreams]

Morning all!
Following on from previous thread, I'm sorry but I need further help!

www.mumsnet.com/Talk/childrens_health/4465815-movicol-to-firm-up-stools?pg=1

I called the continence/bowel service on Monday and explained that I can't get son to drink the movicol and he was refusing water and I was worried about making things worse as he would end up dehydrated. She's agreed to have a week building up trust again by giving no medication, then try again next week. To be honest I felt she wasn't listening to me as she had already said her next client was in the waiting room and she'd called me quickly so didnt have long.

Anyway, please can I ask for advice regarding foods I can give him to help with this overflow?
I'm so confused after googling! I was always told that Weetabix was good for a child so he's been having that for breakfast most mornings (loves his routine, ASD). I am going to attempt to change this though as I've now read that it can cause constipation 🤦🏻‍♀️

Seeds, I've read about flax and chia, I'm going to hide some in his evening porridge (again part of his bedtime routine) but which is best to give and how much?

Prune juice, I'm going to try hide some in his porridge.

Shall I change white bread to brown or seeded bread? To be honest he prob only has bread twice a week.

I have to hide veg in omelettes or scrambled egg but I've read that eggs can cause constipation, is this true?

As an adult I have a tablespoon of flax & 2 teaspoons of chia seeds every day in my breakfast (for the omega rather than bowel issue) so I don’t think a small child would need very much.

I’m also not sure you would be able to hide them -or prune juice-in porridge. My ASD child was very against any change in the way he liked his food. Still is. We used to have to put a spoon of lactulose in his hot chocolate every night. It was explained that ASD children often hold on to their stool. Even with lactulose a bowel movement was still only a weekly occurrence, any longer and we’d have to give movicol too. Only half sachet or it would be explosive diarrhoea.

Syrup of figs?

Would he eat things like mango or soft pears or kiwis? Or any other fruits (perhaps not bananas)?

Baked beans?

Seeded bread or wholemeal better than white.

He's very picky with fruit, only eats the Heinz fruit puree pots and raisins. He likes baked beans and I've been trying to hide different veg (carrots/peas/sweetcorn) in these but he can tell the difference.

Eggs definitely cause constipation for some people. Baked beans are good. What is his liquid intake like? If not great, try jelly, ice lollies made with weak squash, soup- any wet food will help.

Cooked pears are good. Just give those Heinz pear pots if that’s what he likes

He gags at jelly, won't eat ice lollies, and also won't take squash. I've tried so many different bottles/cups/straws etc to try increase water intake
Soup is a good idea though, thank you!
He really likes the puree pots so I think I'll increase to two daily and see how we got on.

I've been back on the phone today to the bowel team to get advice and they've now decided he's not constipated, "it's just how his bowels are", after I explained for the third time that he's always pooed twice daily, not in any pain, normally a 5/6 on the stool chart. She said that alot of ASD children have problem bowels.

I'm still going to try improve his diet and get more fluids in him, if he will let me!