East UP, Bihar, Nepal and Kolkata – Itinerary Advice

Hello Guys

I am all confused with my travel plan... would be great if you can give your suggestions to me.

I have to go to Gaya for my Buddhist rituals, my parents would like to do Buddhist pilgrimage (Buddhist circuit) and my girl friend wants to see Nepal.

23rd of January we fly from Delhi to Kathmandu.
23rd, 24th and 25th we stay and visit Kathmandu (is it possible to include Chitwan here and yet see everything in Kathmandu)
26th we leave for Pokhara by car (how much will it cost?)
26th, 27th and 28th we stay in Pokhara
29th we leave for Lumbini by car (how much will it cost?)
29th, 30th, 31st we stay in Lumbini Monastery and visit Lumbini, Kapilavastu, Kushinagar, Vaishali and Kesariya
1st February leave for Varanasi by train
1st and 2nd in Varanasi and visit Varanasi, Saranath, Kausambi
3rd leave for Bodh Gaya
3rd, 4th, 5th, 6th, 7th and 8th Stay in Gaya and do the rituals
9th Leave for Calcutta
9th, 10th, 11th, 12th Stay and visit in Calcutta and Digha
13th fly back home from Dum Dum

Thanks