Build Advice Best Upgrade Path - New PCs for Office, 2x for Kids, and a VR/HTPC

My PC situation is weird. I've been deferring upgrades to my computers for several years. Here's the current lineup of PCs:

1. I have a computer in my home office. It's one of the 300 Valve Steam Machines from 2013. I've used it as my main gaming rig, but it's almost a decade old now and has been upgraded as far as the current motherboard will allow. As a point of hardware preservation, I don't want to upgrade it further. I'm actually debating putting the new Steam OS on it, but that's a different discussion. The CPU is an i7 4790 and it has a Titan Black in it. It's still capable, but it's really showing its age. Some games complain a bit much and it's unstable in some newer games (Zoo Tycoon, for instance, will crash eventually every time it gets booted). This machine pushes two 1080p monitors. I also use it for various kinds of work, the most demanding being 3D modeling and rendering, and some infrequent video editing.
2. The other rig I use regularly is an HTPC/VR rig in my basement. I run Kodi most of the time or play VR games. It has an i5 9600k and a GTX 1080. It's showing its age as well. It's connected to my 4k projector.
3. My third machine is a 2022 Razer Blade 15 with an i7 12800H, RTX 3070 Ti. I had some weird shakeup stuff happen at work and I found myself needing to get a laptop quickly and start my own business. Then things changed and I'm using my old macbook for work. This leaves me with this Razer laptop that I'm not really using at all.

Those are my three current rigs. Here are my needs/goals.

1. Replace my home office rig (Steam Machine). I don't game as much as I used to, but I would probably game more if I had a better rig. I'm tempted to just retire the Steam Machine and use the Razer laptop. It would be a definite performance boost and I wouldn't have to spend money on a new rig. However, I would like to get a new, bigger monitor. I really like the 5120x2160 monitors, but there aren't any with great refresh rates and they're expensive. I also don't like 32:9 ultrawides. I would like to get back into VR development and video editing. Those both require some beefy hardware and a lot of RAM.
2. Upgrade/replace my HTPC. I'm not sure what a good match for the CPU would be or at what point I'm wasting money. VR is the main gaming I do on this rig. The GTX 1080 drops frames like crazy in newer VR titles and I think there's a decent bit of headroom with the CPU to justify a used GPU that's a good match for it.
3. Get a decent gaming machine for my daughter (age 9). She likes Zoo Tycoon, but it crashes *a lot* when played on my Steam Machine. Something that doesn't crash and could play Zoo Tycoon at 1080p would be good enough.
4. Get a decent gaming machine for my son (age 11). He likes to play games more than my daughter. He's in a robotics club at school, so a laptop might be a good choice for him to be able to debug and reprogram on the go, but that's a consideration, not a requirement.

Other considerations:

1. Value/budget. Budget is probably low-ish. That said, I care more about getting a good value, so if someone said, "This $2500 solution solves all your problems," or, "Don't spend less than $500 on a new GPU right now," I'd like to hear those considerations. Spending a small amount of money poorly is worse than just waiting until I have more money, imo. All that said, I'd like to reuse what I already have as much as possible.
2. The GPU market has been so screwed up since 2020 that I don't even know what to do anymore. Nothing feels like the right price, but it's apparently working for the GPU makers, so I might be the one who needs to adjust.
3. I'm good with DIY and used parts.
4. I like smaller PCs when I have the luxury of choice and have been considering used Zotac mini pcs (or similar) for my kids. The prices for used ones are pretty low. The tradeoff is that I'd be buying stuff that's not super capable and there's probably a better way to spend my money.
5. I think the Steam Machine is either getting retired or will be used for a fun video project where I attempt to install the new SteamOS on it and investigate compatibility of the old hardware. No matter what, I am protective of this machine and it'll stay in my office either in storage or as a functional secondary machine. I don't want it getting damaged out in the rest of my house.

My instinct for a solution is this:

1. Office - New monitor for me. I use it with the Razer laptop.
2. Get an RTX 3080 or 3080 Ti for my HTPC.
3. Some used PCs for my kids. They get my old monitors. One of the used PCs could have the GTX 1080 installed in it.

My other possible solution is:

1. Office - New PC and monitor.
2. Build a new HTPC
3. Give the old HTPC to my daughter
4. Give the Razer laptop to my son

That's it from my brain. What would you all do?

 

ive got 3 kids was kinda in the same position few years ago if i was you id post a wanted post int he classified here and keep an eye oc.uk classifieds as well to get parts

to me the last option is what make sense its kinda what i did

 

Sell the lot and start again.

 

Dang. I was hoping for a little more direction using what I have. I guess I'm feeling pretty cheap right now, haha.

I'll post when I eventually figure it out.

 

I think you've have probably asked people to spend too much time.
Perhaps post for advice on one system at a time for more responses?