Here are some of the lodges/camps we personally recommend as part of our portfolio - places we’ve vetted, visited and enjoyed.
In the modest budget range:
- Mara Kati Kati
- Angata Bologonja
- Serengeti North Wilderness Camp
A bit higher would be:
- River Camp by Karibu Camps
- Lemala Mara
- Mara Mara Tented Lodge
Higher still would be:
- Lemala Kuria Hills
- Sayari by Asilia
- Aurari Camp by Kantabile
- One Nature Mara River
As you mentioned the river crossings, it's worth correcting some of the common misconceptions:
TLDR: Only a portion of the wildebeest migration actually crossover into the Maasai Mara, Kenyan side. Most of it remains on the Tanzanian side throughout the year. The portion that does move to the Maasai Mara generally moves there from around mid-September to mid-November – after which they all start coming back down the eastern side of the Serengeti.
Sometimes they move from early September, other times they linger around for a lot longer. It comes down to weather/rain patterns and an abundance of food. Last year, the last of the herds were still crossing the Mara River on the Tanzanian side all the way into the 3rd week of September.
If your visit isn't towards the tail end of September, I would highly recommend lodges in the Northern Kogatende area of the Serengeti. You get to be close to the migration, close to the predator-prey action.
But if it's towards the tail end of September then its a bit of a coin toss. There's a chance you may be rewarded, but also a chance you'll miss the river crossings.
Personally, if it's in the second half of September, I'd advise guests to skip the Northern Serengeti - accommodation is expensive, adds a lot of miles (unless you are flying) and, as I said, it's a coin toss.
We'd much rather do a proper, confident and rewarding safari with time spent properly in Central Serengeti - where you'll get to see the resident wildlife anyway.