Get your 60 days extention from your single entry non imm O first then go to Savannakhet for the multi entry non imm O. You can get nearly 17 months from it by leaving just before it expires for your last 90 days then another 60 days extention of stay.
The Gym should've given you the required paperwork to get the ED visa at Vientiane and made an appointment for you. I dont believe there's any financial requirements for that visa.
Bad advice! If their stay is more than 30 days they'll need a visa or onward travel within 30 days to board their flight. Much easier and cheaper and less hassle to get the tourist visa before leaving.