Since you are taking your mother, aargee, think about gokarna and murdeshwar. It adds to extra kms. But worth the drive. Sringeri - Horanadu - CKM fall in the route to Bangalore and is better to traverse as they offer you temples to visit and a route which is open. Don't go near Mani/ Puttur/ Sulya. Also Shiradi ghat is fast deteriorating so wouldn't advice drive back through that side.
If you are reaching Udupi on Monday evening I'd suggest you this
Stay at Ramakrishna/ Kediyoor hotel. That will fit your budget. If possible, try get a room in Bhoo Varaha complex. That's real cheap and is very good and is bang next to the temple. There's parking facility as well and the temple complex is just 2 mins away. You get rooms for 150 - 200 bucks. You can have food in Udupi temple itself and there's a good icecream parlour called Dwarika which also serves fast food. And nothing more to state about Mitra Samaj.
Keep Monday evening to enjoy the Navaratna theru going around the car street and visit all the three temples there. All this will be done in 1 hours time with the three temples taking just 15 mins totally for darshan.
Tuesday early morning, go over to Kollur. Enroute you can stop at Anegudde Ganesha temple. They've also opened a new Ayyappa temple around. Kollur is a good 2 hour drive from Udupi during the rains. If you leave by 6:30, with a brief stop at Anegudde, you can expect to reach kollur max by 10 am.
Have darshan at kollur and have food in kollur temple itself and prepare to leave by 2 to come back. Do take a diversion to enjoy the sunset (if visible) at Maravanthe. Also you can admire the sowparnika river that runs along the arabian sea separated only by NH17 for a km or so there.
Come back in the night around 8 - 8:30 back to Udupi and stay put there.
Relax the next morning and do your window shopping and have early morning darshan of udupi again. Set out to Sringeri around 10 after breakfast. You should reach Sringeri by 1 maximum.
There are two routes. One through Hebri - Someshwara - Agumbe. But remember, Agumbe records second highest rainfall in India. Another is through Karkala - Bajagoli - branch off from road towards kudremukha.
I'd suggest Agumbe as the climb is shorter and more exciting! There's a small ganesha temple at someshwara. You can break a coconut there before climbing up. Don't try walking there barefoot, I have a history associated with walking barefoot
Once in sringeri - check in to the choultry rooms. Those are the best. Tell them that you need to stay back to see the puja in the night and you are coming from chennai. They might mostly put you up in Yatri Nivas. Good rooms.
Immediately proceed for lunch at sringeri mutt. Then spend time relaxing feeding the fishes of tunga.
Evening you can go take darshan off all the temples and then cross over to narasimha vana to attend the puja of chandramouleeshwara spatika linga by his holiness. It starts at 9 sharp. If your mother can't walk the distance, there's a route which cars can take. Ask locals for the drive route to narasimha vana.
Stay the night of wednesday at sringeri and proceed to early morning darshan of the temple.
Leave after collecting prasad on thursday (guru's day) from guru and breakfast towards horanadu. Have breakfast from one of the brahmin messes in Sringeri. There are a couple. You get good bonda and idly and great filter coffee.
You leave sringeri towards mangalore, then join the kudremukha - karkala route, take a left towards kudremukha
stop at kudremukha for photo session and proceed to kalasa and horanadu. Kalasa route is always in tatters. But Horanadu Annapurneswari is a good calm temple.
Have lunch there and leave to chikkamagaluru from there.
Stay thursday night at CKM. Friday you can proceed to Hassan leisurely.
Near Hassan are the WORLD famous temples of Belur and Halebidu - the crown jewels of the hoysalas. you can reach Bengaluru or stop before that on Friday night.
Saturday you can wake up and leave outskirts of Bengaluru - take the nice - hit hosur then the GQ and reach chennai comfortably!
So here's the snapshot
Monday eve - Udupi - witness car fetival - visit temples
Tuesday morn - Anegudde - Kollur - lunch at kollur - return to udupi - stop at maravanthe for sunset and sowparnika river snaps
Wednesday morn - visit temples of udupi - have breakfast - leave to sringeri - lunch at sringeri - leisure in the noon - evening darshan of temples - night puja at narasimha vana
thursday - morning collect prasada - have breakfast - leave to horanadu through kudremukha - kalasa - lunch at horanadu - reach chikkamagaluru and stay the night
friday morning - leave to hassan - visit belur - halebid - reach outskirts of bangalore by evening and stay the night
saturday - leave to chennai.
I'd say skip murdeshwara as you are taking your mother. It's a commercial monstrosity now. Nothing more. Gokarna is good, but then I'd say why go the extra in this weather?