The M11 doesn't go anywhere near Ipswich - Suffolk is one of those counties that doesn't have any motorways in its boundaries
If you do follow your suggested route, come off the M11 at Stansted Airport junction and follow the A120 eastbound to the A12 at Marks Tey, then A12 to Ipswich, A14 to south of Ipswich and rejoin the A12 3 junctions after the Orwell Bridge (signposted for Woodbridge & Lowestoft). After a couple of dozen roundabouts, you'll find one on the outskirts of Woodbridge signposted for Orford & Rendlesham (A1152) with a brown tourist Sutton Hoo label.
Boring (and probably most congested) route - M40 & M25 to A12 (junction 28) then A12 northbound to Ipswich as above
It's a long drive for a day trip.