The wire coming into the main panel are very short and to replace the panel I would have to replavc the wire to the meter. Half of the meter is live correct? Just would like to avoid this.

The panel i have now is an older one and breakers are very expensive for it. Double slims are not even available for this. I think it is a commander

I assume those new cc'ts will be 20A for countertops, maybe a dishwasher, garbage disposal, microwave, etc. I'd suggest the same thing as Texas, bite the bullet, put in a 200A service, and a 40 slot panel. That way you can recombine many of those small individual cc'ts into single 15A or 20A cc'ts (depending on wire guage) and have lots of future kitchen options. If you're doing this yourself and are hesitant, you could hire a licensed electrical contractor to do the service entrance and panel upgrade, and you do the rest.

If, as you note, there are a number of circuits with small loads and your house has relatively modest electrical needs (especially those heavy 240V circuits for hot water, dryer, range/oven, heat pump, baseboard heat, air conditioning, hot tub--that sort of thing), then it is entirely possible that your 100A service is fully adequate and you can add more circuits with one or more subpanel(s).

Many if not most moderately sized houses with primarily gas appliances (e.g., furnace, oven, dryer) can operate just fine with more than 20 circuits on a 100amp main service. Then again, some can not.

There are a number of free spreadsheet tools out there to assist you in doing a demand load calculation and many jurisdictions require that this calculation be done before adding to electrical service (e.g., room additions, outbuildings). The information you will need includes: the square footage of the house (to estimate general lighting demand), the face-plate draws (in watts or volt/amps) of major appliances and HVAC systems and the requirements of any additional large loads such as hot tubs, pool heaters, large power tool motors, etc.

The demand load calculation does not merely add up all the power draws; it also takes into account probable diversity of use. (For example, the heat and air conditioning do not usually run at the same time. Similarly, not all of the lights are on at the same time, nor is every receptacle used simulateously.)

If you're interested, I can probably help locate one of the online spread sheets or the written methodology for performing the calculation. Or, one of the sparkies at this site might assist.

Clax66: I had a 2650 sq ft house with full basement that had 100 amp main service, and we never tripped any breakers. It had all gas major appliances.

The number 1 thing you should do is do a proper load calculation as terribletom said. Base your decisions on data, not opinions. If with the kitchen appliance additional loads you are still under 100 amps calculated total load, fine. I'm not an electrician, but I've done a lot of electrical work to various houses, and my understanding is you can put a 40 circuit subpanel in if you want, as long as you don't exceed a total calculated 100 amp load.

So, you can have a subpanel fed from a 100 amp breaker, in your 100 amp old panel. The subpanel can be any size number of circuits, as long as it's rated for the breaker that's feeding it. Some small subpanels only have a 70 amp rating. Most seem to be 100-125 that I've seen.

Do the load calculations. Then if your main service is adequate, you can install a 40 circuit subpanel fed by a 100 amp breaker, as long as your TOTAL calculated load is under 100 amps.

NO, you DO NOT have to derate when using twins. You DO have to make sure your panel will accept them. THIS is the key.
Not all panels will accept twins, tandems, skinnys, etc.

The reason you can feed a panel with a larger breaker is because the panels are rated in large gaps of sizes. Wire and breakers are more definite. It is completely typical to feed a 125A "rated" sub-panel with a 50, 60, 70, or 90 amp breaker.
Besides, the code tells us we can do this. I can find it if you want.

Gil, are you an electrician?

I got my journeyman card in about 1960 from the local IBEW, but I do not see that as any requirement to answer the questions posted here. I also have my electrical and electronic engineering as well.

What is your background?

I made the change to electronics in about 1972. Is my journeyman still valid probably not, don't matter to me.

You might look into the NEC or other code. The local code states no more then 4 tandem breakers unless the box is de-rated, I think I saw that in the NEC, not sure.

Consequently, as stated above, you were mechanically forced to limit the number tandem breakers in a panel, Currently I am not sure if that still holds true.

I asked the local inspector if feeding a 100A sub panel with a 60 amp breaker, he said that would suffice.

No, but having a GOOD clue about CONSTRUCTION and BUILDING electric, and a strong knowledge of the NEC ARE mandatory.
This is not written anywhere but those of us who are versed in this do keep incorrect or erroneous replies in check.

"The local code states no more then 4 tandem breakers unless the box is de-rated, I think I saw that in the NEC, not sure."

That's fine for your local code, just don't post that information as fact. STATE that it is YOUR local code.
NO, it is NO in the NEC.

The slim/double/tandem breakers and the boxes they fit are designed to prevent more than 42 devices in a panel since that is the limit.

If the panel is old enough it may not be listed for use with the smaller breakers.

OP already stated she had 2 hots and a ground.