You'll be regretting saying that when it's pissing it down... ;)
How about, if the weather's lovely, we spend around an hour or two in the Lloyd's (just because everyone knows where it is and where we tend to be), and then move elsewhere? The weather'll still be lovely around 3 or 4, and then we won't have to worry about leaving people behind.
Its easy to find though as its on broad street. an alternative is the James Brindley, which is just by the Hyatt hotel (1 minute walk away!), that has some chairs and tables outisde by the canal.
Just a suggestion, but its may and the weather will probably be good, could we go somewhere that has a beer garden instead?