For starters you have a total allowance of £10,200 each. Up to £5,100 of that can be put into a Cash ISA and the remainder can be put into a Stocks & Shares ISA.

If I had the money spare I would honestly be going for a Stocks & Shares ISA (Self Select - Where you chose where your money is invested) and getting into some low risk funds, some shares, ETFs etc.

Obviously I'm not giving advice, but there are ways to compare Cash ISAs online:

http://www.moneysupermarket.com/savings/isas/cash/

http://www.moneysavingexpert.com/savings/best-cash-isa

http://www.iii.co.uk/isas/?type=cash