The LLC is a real estate rental business. I would want to convert the sep-ira to a Roth with the goal of tax-shielding future earning on these funds.

Yes, you can contribute to a SEP IRA, but if you are self-employed the max amount is 20%, not 25%. This is because your contribution limit is affected by the deduction for self employment tax, which reduces the amount of profit that counts against the 25% limit. And yes - later you can convert the SEP IRA to a Roth IRA, but you will have to pay income tax on the conversion.