TP's will have better dispatch rate, for sure. Just a lot less moving parts and systems. The only two things that can prevent a TP from starting up is a shot battery or a shot starter/generator, pretty much. A spare S/G is easy to carry and power can be had with an external GPU.

Yes you are. My rough estimates for the 421 were ~$650-700/hr. and the MU-2 ~$1100/hr. But, I am also going nearly 100 kts. faster and Jet-A is less than 100LL. In reality, it is not that far apart. My wife tells me the MU-2 is less to operate than the 421 was and she pays the bills. I think it has more to do with the lack of mx bills nearly every month.

It just runs with very few problems.

I think you mean, "no, you're not incorrect"

I went from twin bonanza to King air to Duke.
Twin boys was the most reliable and economical plane I ever owned. King Air was great, but calendar items eat your lunch if you do not fly a lot.
Four years of Duke ownership has cost me about six thousand a year in maintenance and annuals. My continued penchant for upgrades has been expensive and primary cause of AOG. I have never been down for maintenance reasons, but I only fly about 50 hrs or so a year, 100 this year though.
You might consider Lazarus at 125,000 you should have a lot of cash left over from an A-36 sale. I don't think any of the other mentioned options can say that.

Buy a good baron. It will serve your current needs well and allow you to build some multi time. Buy one that will be easy to resell in three or four years. You can evaluate your options and shop at a leisurely pace.

I've lusted over an MU2 or similar for a long time.

Best I can tell, a garret turboprop with an involved owner will cost 1.2x/nm with a 95% confidence interval of 1.1-1.3 and will be available to fly 350 (345-360) days/yr. A 421 will cost 1x (range 0.75-2.5) per nm and be available 330 (180-335) days/year

I am not sure if they are in your price range yet-but a small 208 Caravan is an outstanding family airplane for the owner pilot. I have been flying a 208B Grand Caravan with 10 seats for almost 15 years as a family airplane. We have a potty and unlimited (almost) baggage in the pod. The airplane is very ifr capable and very forgiving. I would much rather have one PT6 than two pistons. I figure 155 knots for 208B, my friend with straight 208 and no pod gets 165 knots or better.

If you go without the pod, there is an extended baggage STC that gives you enough space for 7 passengers with a potty and all of their bags.

In fixing your Bonanza shortcomings, the only thing a Baron gets you is nose baggage. Barons are wonderful, etc., but for my money (which, of course, it isn't ), the added utility wouldn't be worth the cost of upgrading. I'd take a bigger step or none at all.

I have 4 kids that are about ten years older than yours.

We owned a 421 for 5 years and loved it, but I should have gone straight to a TP.

The cost is not that different and the performance is much better.

In icing power is your best defense.

My commander climbs twice as fast as my 421 and can climb as good on one engine as my 421 did on two engines at climb power.

I would skip the piston twin.

The right Navajo (since you mentioned it) could be good. They are hard to find. For your trips it won't be any slower than a 421 other than the 700 mile trip. They are very popular in your part of the country with commercial operators. Check Flightaware.

Speeds are similar to 421C on less gas, but you will be altitude limited.

The 421C is a great bird and if you DO IT RIGHT you will be very happy.

A TP for 200NM trips is overkill. Your weights and fuel requirements (even for the 700NM) will always have you well under gross in a 421C or Navajo type plane. Plenty of margin.

You won't need pressure for 200NM, but it will be very nice on the 700NM flights.

If you want more room a TBone is a great way to go. Be as fast as your bonanza on about twice the fuel burn, but lots of comfort. You could get a great one for the money you would sell the A36 for.

Rare to find them fully deiced though...although they are out there.

Having said that, I would like a turboprop. Mits would be great for you I think.

I'd say your good for 2-3 years with the A36.. Cheap, 6 pax, and effective.. With the young kids your prob pushing the flight of being in the air more than 3 hours..

When your ready to upgrade then the 421C is the machine...

Knowing what you know now, would you have gone straight to the 980, or something else in between?

Merlin IIIB-C with -10 motors, you have have 3 more kids and still be comfortable. No calendar items like the other turboprops. Carry a two bedroom apartment in the luggage area, burns less $ per hour than a 421 at 65 kts faster. Buy midtime garretts and you'll never have to overhaul them in your life. Toilet is enclosed with wood doors.

Knowing what you know now, would you have gone straight to the 980, or something else in between?