Jill, I did this as my first trip - you definitely won't regret it.
With regards to mosquitos - as long as you use something deet based you'll be fine. I normally get bitten wherever I go but they only got me once and that was due to me missing a spot with the deet.
There was no issue with food - all meals are in the lodges, there was plenty of choice and it was all freshly cooked. Bottled water is supplied everywhere as well.
You'll be fine with sandals, the majority of your time is either in the jeep or lodges. I took walking boots but the never came out of my bag, I mainly wore walking sandals or flip flops.
Clothing - lightweight. Things you can layer. Can be chilly early in the morning when going out on drives and cooler in the evenings. I mainly wore Cropped trousers & t-shirts. If you still go to the same lodges, two of them have pools, so remember a swimsuit, there's time to relax by the pool between drives.
They will suggest you take a soft case \ holdall rather than solid suitcase - you travel between lodges in the jeeps so there is not much space and its easier for them to load with soft bags.
Hope that answers some of your questions but it you want to know anything else I'll help as much as I can.
This trip was so much more than i had expected and gave me the courage to book again.
Paula