As far as what days are more crowded, when are you going? The time of year can make a difference, as can whether you are in magic key block out dates, or dates right before certain levels of magic keys are going to be blocked for a while. For example---- we have gone in June several times. We have hit the last weekdays that APs were allowed in the park before being blocked for the summer more than once. Those days are way more crowded than the weekends. If you look at the enchant key calendar this year, they are 1) blocked Friday June 2 to Sunday June 4; 2) open Monday June 5- Thursday June 8; and then 3) blocked from June 9 until August 14. You can expect that last Monday through Thursday they are open before the summer blockout to be way more crowded than the weekends before and after it as people are trying to get a last visit in. When we have gone in June or July-- Mondays always seem to be the most crowded days.
Also be aware that depending on when you go, unlike WDW, the fireworks and Fantasmic may only be shown on weekends.
Park Tickets
Yes-- for 8 days, you would have to buy a 5 day and 3 day ticket. It it is pain because there are a few times we would have liked a 6 day ticket. I would recommend 5 days with hoppers. That is what we usually get and it sounds like you are going to be in California for 8 days and want to do other things. We typically do 5 days at DLR and then either go south to the San Diego area for the rest of our trip, or north to the LA area. We hit the parks around 12 or 1:00 p.m. on arrival day (stay about until DLR close), do 3 full days, and then hit the parks until about 3:00 on departure day. It feels like the right amount of time, although I'm rarely ready to leave Disney and I'm always wishing I could have the rest of that departure day. Unlike WDW, hopping at DLR is about a 5 minute process. The parks are separated by a plaza the size of a football field. We have literally been from the back of DL to the back of CA in 10 minutes. Plus depending on the time of year you are going, often DL is open later than CA, and if you are late night people you can hop over when CA closes and get a couple more hours in at DL. One thing to note is because of the local crowd the 1st two hours in the morning are typically the best park time of the day. Often you can get a lot done in those early morning hours before the parks start filling in (and you are hearing this from night owls that are not morning people by nature).
Dining
For characters at a character meal, you can't beat Minnie's breakfast-- there are different characters there than any of the WDW meals-- and there are often surprises. We've often seen 7 characters during our meal there, and one time we saw 9. Just about every time we have seen Minnie, Chip or Dale or both, Fairy Godmother, Pooh, and Tigger. There are usually at least one or 2 others.
You can see all the menus at the Disneyland website or on the all ears website. I would look for what appeals to you. We typically aren't fans of counter service at WDW and I couldn't spend a week on it. DLR is different- in our opinion they have lots of good counter service options- probably because of the local crowd. We usually enjoy Cafe Orleans, but the menu has somewhat changed. Blue Bayou is similar to San Angel in that a ride goes through, but with a bayou feel, but for the price in our opinion the food has been mediocre-- the menu there has changed recently too. The lamplight lounge brunch is only available on weekends and really hard to get a reservation--- we did it our last trip and thought it was fantastic.
Park to start
I don't think it matters which park you start at if you are talking about 1st day (as opposed to hopping) -especially as you aren't strangers to Disney. You may find that Disneyland feels very familiar but slightly off or like you are visiting the park in a dream as you are used to Magic Kingdom. It feels like it is somewhere you know-- but not quite the same- things aren't quite where you expect them to be.
San Diego Zoo
The zoo will typically be less crowded on weekdays. We've done it on weekends before too. Realize that it is about an hour and half drive from Disneyland. It could take 2 hours if you hit traffic-- but usually going towards the zoo it isn't too bad. I would also highly recommend you take a look at the San Diego Safari Park. They are both great, but my family prefers the safari park to the zoo. The Safari park is owned by the Zoo, but they are about half an hour away from each other. The zoo is right in San Diego and the Safari Park is out a ways--- they are probably both about the same distance drive from Disneyland-- the Safari park may be 10 minutes less to drive from Disneyland.
Universal
Realize although they are only 35 miles apart it can take an hour and a half to two hours to get from Disneyland to Universal. You have to drive through LA to get to Universal and the traffic can be awful. If you are extremely lucky with traffic you might make it in 50 minutes. I've heard that Tuesday-Thursday are the least crowded universal days. We went on a Wednesday in June in 2019 and it was fine. We decided against the VIP tour, but maybe someone else can help you there.
